A New York Police Department veteran was convicted by a federal jury on Monday of assaulting an officer during the Jan. 6 attack on the U.S. Capitol, the AP reported.

Driving the news: Thomas Webster, 56, tackled an officer and grabbed his face mask during the Jan. 6 riot. The jury rejected Webster's argument that he acted in self-defense and found him guilty on all six counts, according to the AP.

• Webster, who was a 20-year veteran of the NYPD, argued that Metropolitan Police Department officer Noah Rathbun instigated the confrontation and punched him in the face. Rathbun testified that he did not punch or initiate the fight with Webster, according to the AP.

The big picture: Webster is the first Capitol rioter to be tried on an assault charge, but his case is the fourth connected to the Capitol riot to appear before a jury, the AP noted.

• At least 820 people have been charged in relation to the Jan. 6 attack on the Capitol, per Insider.

What's next: Webster is scheduled to be sentenced on Sept. 2.