Washington Redskins offensive coordinator Kyle Shanahan explained his treatment of a replacement referee after Sunday's 38-31 loss to the Cincinnati Bengals through a statement released by the team on Monday.
The league is looking into the incident in which Shanahan ran down the official and berated him in the tunnel following the game.
ESPN Radio 980 reported that Shanahan said, "You have no (expletive) balls, you are a (expletive, expletive.)"
Shanahan said in the statement that he was just frustrated and that he was wrong for how he handled the situation.
"When I overheard the official tell the head coach that the game was over after the false start penalty, I tried to explain that the game was not over," he said. "That is what resulted in the unsportsmanlike conduct penalty. I tried to get an explanation of how I could get that penalty when half of the other team was on the field, as well.
"I was frustrated, and in the process of trying to get some answers from the officials, I conducted myself in the wrong way.
"I ask our players to hold themselves to a high standard and be accountable, and I know that I'm accountable for my actions, as well.
"I know that I need to handle those situations better in the future. My emotions got the best of me, and I know it's my responsibility. This will never happen again."
After a penalty was called on the Redskins with seven seconds left in the game, at least one official deemed the game over after incorrectly ruling there was a 10-second run-off of the clock. Shanahan was then penalized for unsportsmanlike conduct while arguing against the incorrect call.
After the mistake was corrected, referees spotted the ball incorrectly by five yards on the Shanahan penalty, according to the Washington Post.