Woo had an argument with his live-in girlfriend on the afternoon of April 26, 1982. Enraged, he left the house and went to the police armory, where he began consuming large amounts of whiskey. After becoming heavily drunk, he raided the police armory of its weapons and built a personal arsenal. Woo then stole a single rifle and some grenades and left the armory around dinner time. Walking from house to house, he abused his position as a police officer to make people feel safe and gain entry into their homes. Then he shot the victims, or killed the entire family with a grenade. He continued this pattern for a full eight hours.
Once Woo had shot a certain number of people in a village, he would run to another nearby village to continue the massacre. In the early hours of April 27, after rampaging through five villages in Uiryeong county, Woo took his final two grenades and strapped them to his body. He took three people hostage and set the grenades' fuses, killing both himself and his final victims.