NEW YORK - The city's police commissioner didn't hold back Monday while responding to criticism from the head of the sergeant's union.

Sergeants Benevolent Association President Ed Mullins had blasted James O'Neill for the way he handled the recent water bucket attacks on officers.

He claimed that O'Neill was condoning disrespect toward cops by not having a stronger response.

The commissioner fired right back at Mullins during an unrelated event Monday.

"I haven't seen that guy around in any department function, I've been a PC for almost three years. He's a bit of a keyboard gangster. We're here to keep the city safe. We're here to keep the cops safe. And if you want to second guess us, think we don't care about cops, you're dead wrong You're in the wrong business. He should rethink his position," O'Neill said.

As one might expect, Mullins did not like that.

He called O'Neill a funny guy in a tweet, and told him to get out of the mayor's shadow.