May 3 (UPI) -- A Secret Service agent shot during an incident at the White House Correspondents' Association Dinner was hit by a pellet from a shotgun fired by accused assailant Cole Allen, a U.S. prosecutor said Sunday.

An initial investigation of the violence at last week's Washington D.C. event failed to confirm who had fired the shot that was stopped by the agent's bulletproof vest, leading to speculation the agent could have been hit by friendly fire as a heavily armed Allen tried to barge into a hotel ballroom during an alleged assassination attempt against President Donald Trump and Cabinet members.

But U.S. Attorney for the District of Columbia Jeanine Pirro claimed Sunday further analysis has revealed the agent was indeed struck by a projectile fired from a weapon allegedly carried by Allen.

"We have been able to determine which gun it was," she told CNN's State of the Union. "First of all, there is video of the defendant shooting at the Secret Service agent. There is also the agent who will tell you himself that he was shot at and then he returned the fire."

But more importantly, Pirro said investigators have now established that "a pellet that came from the buckshot from the defendant's Mossberg pump-action shotgun was intertwined with the fiber of the vest of the Secret Service officer.