After the German and Russian invasion of Poland in 09.1939 and the start of World War II, after the beginning of the Russian occupation, continued his philosophical and theological studies at the Franciscan College in Lviv. Despite the Russians closing the Polish John Casimir University in Lviv, where the Faculty of Theology had operated till 29.10.1939, and the prob. necessity of conducting some lectures clandestinely, the College operated throughout the entire period of Russian occupation. Studies did not follow an annual cycle, but after 8 or 9 months of study, without vacations, the next year began. Seminarians were also forced to attend a Russian language course for conscripts and pass an exam on the practical requirements for these conscripts.

After the German attack on 22.06.1941, on their erstwhile ally, the Russians, and the beginning of the German occupation, was ordained a priest in 1942 and sent to the Franciscan monastery and Roman Catholic parish in Leshniv, c. 90 km northeast of Lviv. Administratively, Leshniv found itself in the Germ. Landkreis Zloczow (Eng. łoczów County) in the Germ. Distrikt Galizien (Eng. District of Galicia), German‐occupied and run quasi‐state called the Germ. Generalgouvernement (Eng. General Governorate), i.e. GG. In 1939, the town had an estimated population of c. 1,900, of whom c. 30% were Roman Catholic Poles, c. 60% were Ukrainians, and c. 200 Jews.

Arrived in Leshniv when the Germans were finalizing preparations for the genocidal plan Germ. «Endlösung der Judenfrage» (Eng. Final Solution of the Jewish Question), in the GG known under the German codename Germ. «Aktion Reinhardt» (Eng. Operation Reinhardt). From 13.01.1942, in Brody, c. 20 km away, an open ghetto operated. C. 6,500 Jews were detained there. On 19.09.1942, the Germans, with the participation of the Ukrainian collaborationist Germ. Ukrainische Hilfspolizei (Eng. Ukrainian Auxiliary Police), in some regions also referred to as Germ. Schutzmannschaft (Eng. Protection Battalions), i.e. Schuma, transported c. 2,500 Jews to the Germ. Vernichtungslager (Eng. Extermination camp) VL Belzec, where they were murdered. C. 300 were murdered during the round‐up operation, still in Brody. At the end of 11.1942, another 2,500 victims were transported to VL Belzec. A few weeks earlier, on 10.11.1942, the ghetto was closed, i.e. surrounded by a barbed‐wire fence guarded by the Germ. Ukrainische Hilfspolizei.

On 02.12.1942, c. 2,000 Jews from nearby villages and towns, including Leshniv, were brought to the ghetto. The number of detained Jews increased to over 5,000. C. 1,000 of them died in the winter of 1942‐1943, among other things as a result of a typhus epidemic. Starting on 21.05.1943, the Germans began the liquidation of the ghetto, which lasted about a month, murdering c. 100 Jews on the spot and deporting the rest to extermination camps, including KL Lublin (Majdanek).

As a result, according to German sources, in 1943 only 1,258 people lived in the deserted Leshniv.

Was there when, in 02.1943 Roman Shukhevych, nom de guerre „Taras Chuprynka”, the chief commander of the Ukrainian, genocidal OUN/UPA organisation, who in 1941 was a member of the Ukrainian Germ. Sondergruppe Nachtigall (Eng. Special Group Nightingale) — a unit of the Germ. Wehrmacht (Eng. Armed Forces) that took part in the German attack on Russians in 1941, accused of participating in the Jewish pogrom in Lviv in 1941 — and later a member of the Germ. Schutzmannschaftsbataillon 201 (Eng. 201st Protection team Battalion) — responsible for the murder of Jews and civilians in the territory of Belarus — issued an order: „The extermination operation should be carried out according to the following principles: Polish villages are to be burned, and their populations massacred. Attacks on towns will take place in broad daylight, not at night. In mixed villages, the Polish population alone should be liquidated, and farmsteads should be burned only if they are 15 meters away and when there is no risk of the fire spreading to neighboring Ukrainian buildings. The Ukrainian population will receive instructions as to where to gather during the attack […] For every Ukrainian murdered, whether by Poles or Germans, 100 (one hundred) Poles will be executed”.

It was the de facto signal for the commencement of the «Genocidium Atrox» — i.e. the genocide perpetrated by Ukrainians, known as „Volyn genocide”.

Immediately afterwards, in 03.1943, the UPA issued an appeal addressed to members of the collaborative German Ukrainische Hilfspolizei, which participated in the implementation of the Germ. «Endlösung der Judenfrage» — to desert and join the UPA. Perhaps as many as 10,000 Ukrainians did so.

The tactics of the genocidal Ukrainians were detailed in an order issued by the UPA commander in Volyn, neighboring Germ. Landkreis Zloczow, Dmytro Klachkivsky nom de guerre „Klym Savur”, from 06.1943. Anticipating Germany's defeat in the war with Russia, explained and ordered: „We should carry out a major operation to eliminate the Polish element. When the German troops withdraw, we should use this opportune moment to eliminate the entire male population aged 16 to 60 […] We cannot lose this fight, and we must weaken Polish forces at all costs. Forest villages and villages located near forest massifs should disappear from the face of the earth”.

Volyn was drenched in Polish blood. Tens of thousands of Poles were murdered by the Ukrainians — with German passivity — in an extremely barbaric manner. Hundreds of villages were burned.

When at the turn of 1943/1944 it became clear that Germany was losing the war in the East — on 24.12.1943, a major Russian offensive known as the Dnieper–Carpathian Operation began — the OUN/UPA decided to extend the «Genocidium Atrox» extermination plan to the Germ. Distrikt Galizien and Germ. Distrikt Krakau. Until then, the groups operating there were mainly — so as not to „annoy” the Germans — units operating under the euphemistic Ukrainian name Ukr. Українська Народна Самооборона (Eng. Ukrainian National Self‐Defense), i.e. UNS, reinforced by deserters from the Germ. Ukrainische Hilfspolizei and Schuma, seasoned in the genocide of Jews. The Ukrainian génocidaires, i.a. formed the OUN/UPA operational group „UPA‐West”, under the command of Vasyl Sydor, nom de guerre „Shelest”, who ordered „to constantly attack Poles until they are completely exterminated from these lands”.

And it was then that was transferred to Sokal, in the Germ. Landkreis Kamyanka Strumilova, part of the Germ. Distrikt Galizien within the GG. This happened right before the German–Russian fighting front reached Leshniv, because it was precisely on 17.04.1944, when the Russian offensive stopped for the spring period i.a. on the Leshniv‐Brody line, i.e. the Dnieper–Carpathian Operation ended.

Became the guardian of the Franciscan monastery in Sokal, at the same time becoming the administrator of the local parish, as well as the administrator of the Waręż parish, c. 15 km away. Arrived in the town, situated on the right bank of the Bug River, which had a similar history to Leshniv during World War II. In the years 1939‐1941, Sokal — which in 1939 was inhabited by an estimated 13,000 people, including c. 35% Poles, c. 24% Ukrainians and c. 40% Jews — was occupied by the Russians. And then, on 22.06.1941, on the first day of the German attack on the Russians, it was captured by the Germans. In the years 1941‐1943, the Germans — with the cooperation of Ukrainians of Germ. Ukrainische Hilfspolizei — murdered the Jews. On 17.09.1942, they transported c. 2,000 of them to VL Belzec. On 15.10.1942 the ghetto was established, controlled from the outside by the Germ. Ukrainische Hilfspolizei, and inside by the Germ. Jüdischer Ordnungsdienst (Eng. Jewish Police Service). On 28.10.1942, another 2,000 Jews were deported to VL Belzec. The rest — c. 4,000 people, some of whom died in the winter of 1942‐1942, i.a. from the typhus plague — were murdered on 27.05.1943.

In 1943, according to German sources, 9,573 inhabitants remained in Sokal.

On 19.07.1944, after renewing offensive, during Lviv–Sandomierz operation, the Russians entered the city. The Russian occupation began.

The genocidal UPA continued to implement its plan to exterminate Poles, but de facto deprived of German protection, it also had to fight with Russian rear units that were growing in strength every day. In the vicinity of Sokal, the «Genocidium Atrox» was implemented by the OUN/UPA military district WO‐2 „Bug”, commanded by Vasyl Levkowich, nom de guerre „Voronyj”, who issued the order to „liquidate strong and active Polish populations”.

Despite this, continued his ministry in his parish. Access to Sokal itself, situated on the right bank of the Bug River, was however increasingly limited. The Franciscan monastery was located on the left bank of the Bug, opposite the city, in a settlement called Zvirka. The Bug River was established by the Russian occupiers as the border between the territory of Ukraine, under their direct occupation, and the new state entity, Commie‐Nazi Poland, known as the prl, ultimately to be governed by Polish traitors, Russian collaborators.

Crowds of Poles fleeing from the east — from the genocidal OUN/UPA, as well as those expelled from their homelands by the Russians as part of the deportation of Poles to the west, in accordance with a standard Russian practice for resolving social and national issues — began to gather in his monastery.

To feed the unfortunate, traveled to nearby villages and towns in search of food. And genocidal OUN/UPA units prowled the roads.

On 04.05.1945, on the third Sunday of Lent, traveled to Krystynopil, c. 10 km south on the left bank of the Bug River, to lead retreat prayers. The next day, set off on his return journey (alternatively, could have traveled to Krystynopil that day if the retreat was just beginning). According to other sources, was heading towards Lviv for food.

In the village of Dobryachyn, c. 3 km from Krystynopil, inhabited mainly by Ukrainians, was fired upon.

Tried to escape westward along a path leading to the village of Boratyn, which intersected the Krystynopil‐Sokal railway line.

Several thugs from the genocidal OUN/UPA on horseback chased him.

He was caught.

Prob. was tortured — with a saw.

His body was never found — was prob. thrown into a pond.

Two other Poles who accompanied him were killed along with him.

The crime may also have been committed by agents of the genocidal Ukr. Служба Безпеки (Eng. Security Service), i.e. SB OUN, tracking down political and ideological opponents of the OUN, physically liquidating them, and also participating in the murders of the Polish population, whose commander was the génocidaire Mykola Arsenych, nom de guerre „Mykhailo”. Sources indicate that „SB OUN could only issue death sentences to "enemies of the Ukrainian nation" […] For minor offenses, the so‐called buki were used, i.e. beatings with beech sticks from 10 to 50 strokes. Major offenses were punished by death. The sentence was carried out by shooting or hanging […] some group commanders "chopped off the heads of their victims"”. The SB OUN was founded in 1940, under the watchful care of the Germans, and training was conducted, among others, in Zakopane, at the „Stamary” hotel. According to the contemporary website of this hotel, „the training included the principles of sabotage, Gestapo methods of interrogation and methods of killing”. At the same time, i.e. on 20.02.1940, in Zakopane, at the „Pan Tadeusz” (Eng. „Sir Thaddeus”) and „Telimena” villas, the third so‐called „thematic conference” of the Germ. Geheime Staatspolizei (Eng. Secret State Police), i.e. Gestapo, and the Russian Rus. Народный Комиссариат Внутренних Дел (Eng. People's Commissariat of Internal Affairs), i.e. NKVD, two genocidal allied organizations, debating cooperation and ways of combating and exterminating Poles in the territories they occupied. In Zakopane, all these undertakings were supervised by the Gestapo, which had its headquarters in the „Palace” villa, where Polish patriots were being murdered.

Father Mucha has no monument. However, the génocidaire Roman Shukhevych was on 12.10.2007 posthumously awarded the title of Hero of Ukraine. On 10.12.2017, on behalf of the „Coordination Council for the Commemoration of Decorated Knights of the OUN and UPA”, génocidaire Vasyl Sydor was posthumously awarded in Lviv the Silver Cross of Military Merit of the UPA, 1st Class (No. 009). The génocidaire Mykola Arsenych even received the Golden Cross of Military Merit of the UPA, 2nd Class, confirmed by the Lviv Regional Council on 05.03.2008, and because survived 25 years in Russian labor camps, after his return was granted an apartment in Lviv along with financial support. In 2007 became also an honorary citizen of the town of Sheptytskyi, formerly Krystynopil, in 1939 with Polish majority, in whose expulsion and murder played a significant, though probably indirect, part. In several locations, monuments and commemorative plaques have been erected to these Lat. „hostis humani generis”, the schools were named after them.

Lat. „O Tempora! O mores!”.

The genocidal actions of Ukrainians and Russians were complemented on 15.02.1951, when both the left‐bank part of Sokal with its Franciscan monastery and Krystynopil were taken over by the Russians — „under an interstate agreement” between Soviet Russia and the Russian Polish Republic „prl”. In exchange for territory rich in coal, the prl received a mountainous, forested area near Ustrzyki Dolne in the Bieszczady Mountains.