(NewsNation) — A potential FBI interview with former President Donald Trump could be critical for the investigation into the July 13 assassination attempt that left him with a graze wound to the ear, a former U.S. Secret Service agent said.

Trump has agreed to be interviewed by the FBI as part of an investigation into the shooting that killed one attendee and seriously injured two others earlier this month at a Butler, Pennsylvania, rally. The expected interview with the 2024 Republican presidential nominee is part of the FBI’s standard protocol to speak with victims during the course of their criminal investigations, the Associated Press reported.  

“It’ll be important to them to get from his perspective how things unfolded and what happened,” said Donald Lane, a former U.S. Secret Service agent for former Presidents George H.W. Bush and Bill Clinton.

Investigators on Monday said the gunman researched mass attacks and explosive devices before the rally shooting. A counter-sniper with local law enforcement also noticed the gunman about 1 1/2 hours before the shooting, the New York Times reported.

“I’ve said from the beginning I believe this young man falls more into the category of a school shooter or a person who wants to do mass destruction,” Lane said. “I believe he put this plan together very quickly and identified a target who was going to be in town, so it was convenient for him.”

The FBI has instructed the Trump campaign to refrain from hosting outdoor events while the investigation is underway.

“I have no doubt that now they could do an outside site,” Lane said. “I think right now, they’re trying to get to the bottom of it and have a few more answers, perhaps, before they do that.”