On the afternoon of December 30, 1974, Anthony F. Barbaro, a 17-year-old honor student and member of the Olean High School rifle team, drove to the school, which was closed for Christmas break. He entered through an unlocked side door, went to the third floor, and set a coke bottle filled with gasoline alight, triggering a fire alarm. Unable to open the locked student council room door, he shot off the lock and barricaded himself inside.
When custodial staff responded to the fire alarm, Barbaro, identified as the gunman, shot and killed Earl Metcalf, 62, a school employee who approached the student council room despite a colleague's warning that gunshots had been heard. Barbaro then began shooting from the third-floor windows at people outside the school. As fire trucks, local police, and New York State troopers responded, Barbaro continued firing, ultimately discharging 31 shots. He fatally shot Neal Pilon, 58, a Columbia Gas Co. employee crossing the street outside the school, and Carmen Wright Drayton, 25, who was six months pregnant with twins and was shot in the head while driving past the school in her car. Both were pronounced dead on arrival at Olean General Hospital. Eleven others were wounded, including seven with gunshot injuries and four with injuries from flying glass; eight of the wounded were Olean firefighters who had responded to the initial fire alarm.
By early evening, police and a National Guard tank had surrounded the school to assist with removing the injured. Before nightfall, two New York State Police officers entered the building and threw tear gas into the student council room, where Barbaro was found unconscious while wearing a defective gas mask. He was taken to a hospital, found uninjured, and then transferred to the Olean City Jail.
Barbaro was arraigned on December 31, 1974, on three counts of second-degree murder, six counts of first-degree assault, and five counts of first-degree reckless endangerment. Investigators recovered homemade smoke bombs, bomb-making materials, and a journal detailing his plans from his bedroom. In April 1975 he pleaded not guilty by reason of insanity, but two court-appointed psychiatrists found him competent to stand trial. He was later moved to the Cattaraugus County Jail in Little Valley, and a grand jury was seated on October 21, 1975.
On November 1, 1975, before his trial concluded, Barbaro hanged himself with a bedsheet in his cell. The Cattaraugus County coroner ruled the death a suicide. He left three notes, including one describing regret over his life and stating that he saw no survivable outcome whether he was convicted or acquitted. Police stated they found no clear motive for the shooting, though a teammate recalled Barbaro previously discussing a desire to stage an armed standoff with police.