On August 21, 1992, a number of people were evacuated from the Trnopolje concentration camp to be transported to Bosnian government-controlled territory in central Bosnia. However, on Mt. Vlašić, some 200 to 250 men (228 according to the UN) were selected and separated from the main group, and crammed into two buses by a group of reserve Bosnian Serb paramilitary policemen from Prijedor (so-called "Intervention Squad", also known as "Mice" or "Red Berets"). The men were told they would be exchanged for the prisoners held by the Bosnian government forces.
Instead, they were shot at the edge of a ravine, one-by-one or in groups of three, and thrown down the 100-meter high cliff. Twelve of them, however, survived the shooting and the fall down the abyss. A survivor recalled:
Immediately after the fall, I jumped to my feet and started running to a nearby forest. When I reached the forest I turned around and saw another man running my way. I waited for him and then we ran together to a nearby water mill. From there I looked down the road. People were still falling. Farther in the distance I saw that the first bus had stopped, but it was very far away and I couldn't tell what was going on. Later, a survivor told me that they were taking men off the bus one by one and killing them. When they killed about half the men on the bus, they got bored with doing them one by one, so they killed the rest of the passengers three at a time. After the execution was complete, the Serbs left with the buses. Since the cries could still be heard, I went back to the corpses. I came to about ten meters from the corpses, when I heard buses again. I hid behind the rock. The buses stopped. Then they started shooting the corpses from above. They threw a few hand-grenades before they left, too. When they left, I ran away and did not come back.
Seven of the survivors were found by the members of the regular Army of Republika Srpska. The soldiers rescued them from the police and filed a report on the "terrible crime against civilians", but the prisoners were not immediately released and some faced further abuse while treated for their wounds.
The police unit responsible for the atrocity committed a number of other crimes in the area, including some against the local Serbs.
Only one person, the ringleader Darko Mrđa arrested in 2002 , has been convicted on two counts of crimes against humanity (extermination and inhumane acts) and one count of violations of the laws or customs of war (murder), including the Korićani killings. Mrđa was most likely ordered to commit this crime by Simo Drljača, the chief of police in Prijedor who was later shot and killed in 1997 by the SFOR soldiers during an attempt to arrest him. As of 2007, other executioners are still at large and show no signs of remorse.