On this day in 2007, in one of the deadliest shootings in U.S. history, 32 students and teachers die after being gunned down on the campus Virginia Tech by Seung Hui Cho, a student at the school who later dies from a self-inflicted gunshot wound.

The violence began around 7:15 a.m., when Cho, a 23-year-old senior and English major at Blacksburg-based Virginia Tech, shot a female freshman and a male resident assistant in a campus dormitory before fleeing the building. Police were soon on the scene; unaware of the gunman’s identity, they initially pursued the female victim’s boyfriend as a suspect in what they believed to be an isolated domestic-violence incident. However, at around 9:40 a.m., Cho, armed with a 9-millimeter handgun, a 22-caliber handgun and hundreds of rounds of ammunition, entered a classroom building, chained and locked several main doors and went from room to room shooting people. Approximately 10 minutes after the rampage began, he committed suicide. The attack left 30 people dead and another 17 wounded. In all, 27 students and five faculty members died as a result of Cho’s actions.

Two days later, on April 18, NBC News received a package of materials from Cho with a time stamp indicating he had mailed it from a Virginia post office between the first and second shooting attacks. Contained in the package were photos of a gun-wielding Cho, along with a rambling video diatribe in which he ranted about wealthy “brats,” among other topics.

In the aftermath of the massacre, authorities found no evidence that Cho, who was born in South Korea and moved to America with his family in 1992, had specifically targeted any of his victims. The public soon learned that Cho, described by ex-classmates as a loner who rarely spoke to anyone, had a history of mental-health problems. It was also revealed that angry, violent writings Cho made for certain class assignments had raised concern among some of his former professors and fellow students well before the events of April 16.

In 2011, Virginia Tech was fined by the U.S. Department of Education for failing to issue a prompt campus-wide warning after Cho shot his first two victims. School officials sent an email notification about the dorm shooting to students and faculty at 9:26 that morning. According to the Department of Education, the message was vague and did not indicate there had been a murder or that the gunman was still at large.