Cole Tomas Allen opened fire, the FBI said

The officer returned fire, firing multiple rounds and stopping the suspect before he could reach the crowded event space.

Authorities have insisted the outcome could have been catastrophic had he not been stopped.

The FBI described the alleged attack as a calculated act of political violence that endangered the lives of hundreds, noting that Allen was armed with a shotgun, a loaded .38 caliber pistol, knives, daggers and additional ammunition at the time of his arrest.

But the chilling plot didn’t begin that evening.

Investigators allege that Allen’s alleged scheme unfolded over several weeks, beginning in early March, after the president publicly confirmed he would attend the annual dinner.

On April 6, prosecutors allege, Allen began researching the event online before securing a hotel reservation at the Washington Hilton, the same location where the high-profile meeting took place.