Author of Columbine, expert on school shootings.

Groundhog Day from hell. Sadly, I’m discussing the horror: AC360 at 8:30pm, possible phoner with Chris Hayes 8pm, i24 news at 9:40. Tomorrow New Day on CNN, WGN-TV morning show, HLN at 11am, Nicole Wallace on MSNBC in the 4pm hour.

— Dave Cullen (@DaveCullen) February 15, 2018