Seung-Hui Cho

Seung-Hui Cho was the perpetrator of the "Virginia Tech massacre", which is currently the second-deadliest massacre at an educational facility (behind the the Bath School bombings) and the deadliest shooting committed by a lone gunman in U.S. history.

Modus Operandi
Cho shot his victims with two semiautomatic pistols, one a .22 caliber Walther P22, the other a 9mm Glock 19. He used hollow-point bullets as ammunition; said bullets inflict more damage to the tissue by expanding upon entry. Cho also brought along a knife, which he presumably intended to use during the massacre under the occasion that he ran out of ammunition, but the weapon was never used.

Fatalities

 * The West Ambler Johnston Hall shooting:
 * Ryan Clark, 22
 * Emily Hilscher, 19
 * The Norris Hall shooting:
 * Minal Panchal, 26
 * Gobichettipalayam Vasudevan "G.V." Loganathan, 53
 * Jarrett Lane, 22
 * Brian Bluhm, 25
 * Matthew Gwaltney, 24
 * Jeremy Herbstritt, 27
 * Partahi Lumbantoruan, 34
 * Daniel O'Neil, 22
 * Juan Ortiz, 26
 * Julia Pryde, 23
 * Waleed Shaalan, 32
 * Jamie Bishop, 35
 * Lauren McCain, 20
 * Michael Pohle, Jr., 23
 * Maxine Turner, 22
 * Nicole White, 20
 * Liviu Librescu, 76
 * Jocelyne Couture-Nowak, 49
 * Ross Alameddine, 20
 * Austin Cloyd, 18
 * Daniel Perez Cueva, 21
 * Caitlin Hammaren, 19
 * Rachael Hill, 18
 * Matthew La Porte, 20
 * Henry Lee, 20
 * Erin Peterson, 18
 * Mary Karen Read, 19
 * Reema Samaha, 18
 * Leslie Sherman, 20
 * Kevin Granata, 45

Injuries

 * The Norris Hall shooting:
 * Colin Goddard
 * Emily Haas
 * Katelyn Carney
 * Derek O'Dell
 * 11 other unnamed people
 * Note: There were six more reported injuries, but the victims didn't suffer any wounds inflicted by Cho; instead, they were injured after jumping from second-story windows to escape.

In Criminal Minds
Cho was mentioned at the beginning of Jump Cut, when Hotch is doing paperwork relating to school shooters.