May 7, 2019: STEM School Highlands Ranch – Two suspects reported in custody and seven to eight people reported injured.

Dec. 13, 2013: Arapahoe High School, Centennial – A student entered the school carrying a shotgun looking for a particular teacher, who left the building. The shooter shot one student before lighting the library on fire and killing himself.

Feb. 23, 2010: Deer Creek Middle School, Littleton – In the parking lot of a middle school, a man shot a rifle wounding two eighth-grade students. He was tackled by faculty and arrested. The man was found to be legally insane and is in a state mental hospital.

Sept. 27, 2006: Platte Canyon High School, Bailey – An adult fatally shot 16-year-old Emily Keyes and then himself after taking hostages.

April 20, 1999: Columbine High School, Jefferson County – Two male high school students killed 12 students and one teacher and wounded 24 other people before committing suicide in the school library.