Karl Pierson had grown angry and made threatening remarks before he shot a student and himself in a Colorado high school. NBC’s Ron Mott reports.Dec. 16, 2013
UP NEXT
Memorial Day celebrations across the U.S. honor military service and sacrifice
01:56
Former Vietnam POWs reunite 50 years after their return to the U.S.
02:30
Partial building collapse in Davenport, Iowa leaves community desperate for answers
03:00
Some electric car companies to stop including AM radios in their vehicles
03:00
Biden and McCarthy reach deal to raise the debt ceiling
02:26
Recovery efforts underway after Iowa building collapse