The incident happened right after the Bears win over the Packers.
Collins says it was because of a racial slur. He has apologized for what he calls losing his cool.
He admits his performance in-game played a role in the Packers losing, but says that was no excuse for the way he says he was treated by a Chicago fan after the game at Soldier Field.
Collins is a veteran linebacker and two-time Pro Bowler, but Monday night, his actions off the field were less than award-winning.
After losing to the Bears in a 20-to-17 contest, Collins is seen yelling at a fan, and then it appears as though he throws his mouthguard into the stands.
Collins says he was reacting to a fan spitting on him and calling him a racial slur.
Packers Head Coach Mike McCarthy says he supports Collins 100 percent, but he does admit it would be wise for players to avoid confrontations with fans.
"You don't want to get into interaction, particularly with opposing fans," said McCarthy. "It is an emotional time, particularly after the game, and I think it is something we can learn from."
Chicago Bears linebacker Lance Briggs says that while he has been taunted before, he has never been the victim of a racial slur.
Briggs says he understands the intense fans and the rivalry with Green Bay, but that yelling a racial slur is crossing the line.
"You're already a little beat up, you are a little down - to hear something like that from a fan, there are gonna be times when a guy will lose his cool," said Briggs. "I understand that."
According to a Bears spokesperson, the team is reviewing all the facts and monitoring the situation.
Packers security backs up Collins's details of what happened.