The two men said Officer Rivera waved his gun at them and told the friends to "back off."
The report said that Officer Rivera began to lose the grip on his gun.
The name of Officer Rivera's estranged husband was not made public.
Officer Rivera, 37, was charged with covering up for him.
Officer Rivera said she did not know an officer had been shot, and found out at the police station.
"I was also the biggest guy out there," Officer Rivera added.
But investigators and other police department officials say Officer Rivera was a problem from his first year on the force eight years ago.
He asked them to go and speak to Officer Rivera.
Officer Rivera and her husband live less than two blocks from the site of the shooting.
Officer Rivera lives there with her husband and three young boys, neighbors said.