Colorado State defensive back Henry Blackburn is on the receiving end of death threats after laying an controversial hit on Travis Hunter during Saturday's game ... and now, university police tell TMZ Sports an investigation into the hateful messages is underway.
Blackburn received a ton of heat for his massive late hit on the Colorado receiver in the first half of the Rams vs. Buffaloes matchup... which left Hunter sidelined for weeks with a lacerated liver.
Some looked at Blackburn's tackle as targeting .