(NewsNation) — Blind spots and a possible mistaken identity aided the shooter in last Saturday’s assassination attempt on former President Donald Trump, according to a former Navy SEAL who now serves in Congress.

“The shooter got really lucky,” Rep. Dan Crenshaw, R-Texas, told NewsNation’s “The Hill.”

“He climbed up an AC vent, and he was out of view of where those officers were who were actually in the building complex,” he said.

Crenshaw also defended law enforcement over reports the shooter was seen about one hour before shooting at Trump.

“They didn’t see him with a weapon. He was noticed an hour before with a range finder. Many Trump supporters probably have something like a range finder. They want to see their president. So he’s a person of suspicion, but you just don’t go shooting the guy,” Crenshaw said.

Secret Service sources tell NewsNation the working theory right now is that the countersniper didn’t initially shoot the gunman because the sniper thought the gunman was a police officer.

Crenshaw says a part of the story not getting enough notice is how quickly events happened once officers confronted the shooter.

“The problem is: The police confronted him, the shooter turned his weapon on them, the police fell off the roof. And then the shooter quickly scurried up, silhouetted himself on the apex of the roof and began shooting — immediately upon which time the Secret Service countersnipers shot him,” he said.

Despite that, Crenshaw says there were, indeed, security failures.

“You have to completely cordon off an area that’s only 150 meters from the target. That’s where (the investigation) will lead. That’s where the failure will be.”

Crenshaw says he expects the investigation to focus on Secret Service protocols and whether agents followed them.

“I would assume that Secret Service protocols that a building complex only 150 meters away with a clear line of sight to the president would have a lot more resources than just than just local police,” he said.

However, Crenshaw said that local law enforcement is always a part of a Secret Service protection operation: “Secret Service never has enough people for anything. They always, always delegate some of the responsibilities to local and state authorities, and they work well together.”

But Crenshaw warns that doesn’t absolve the agency of responsibility.

“Secret Service has to do a better job vetting who might be in charge of that particular area. They can’t just look away.”