A former Secret Service agent believes it’s “impossible” that former President Trump’s security detail would not have noticed the rooftop where a gunman opened fire in Saturday’s assassination attempt in Butler, Pennsylvania.

In an interview with KTLA 5 Morning News, Christopher McClenic said agents would have conducted walkthroughs before Saturday’s event, during which they would have had the opportunity to stand at the podium site, look out where the crowd would be and see the rooftop and any other areas of concern.

“That said, I find it impossible. Impossible to believe that a Secret Service agent, a supervisor, no one did not notice that that site, that area needed to be covered,” McClenic told KTLA’s Frank Buckley and Jessica Holmes.

“I don’t want to say whether it was covered by an officer or agent, or it should have been and that person wasn’t there, but absolutely it should have been covered and would have been covered in any other circumstance,” said McClenic, who described the incident as a tragic failure.

“There’s a lot of responsibility out there. I will say that the rooftops, the overhangs, that really does concern me that that wasn’t covered, or if it was covered, it obviously wasn’t covered correctly,” he said.

McClenic also said that, at minimum, a local police officer should have been posted, and possibly a special agent from the Secret Service should have been put there.

“I think the tragedy of it all is that this rooftop should have been manned; it should have been posted,” McClenic said. “I would suspect some leadership changes. I would suspect some reinforcement of training and I would suspect some significant policy changes as well.”

The former agent referenced the many changes that occurred when a man jumped the White House fence in 2014 and entered the East Room with a knife during Barack Obama’s presidency.

“And that of course was not nearly as tragic as this event,” McClenic said.

Trump was tackled and rushed off stage after being struck in his right ear by the bullet. He was said he was “fine” shortly after the shooting and is expected to speak during this week’s Republican National Convention.

The gunman, identified by the FBI as 20-year-old Thomas Matthew Crooks, was killed by the Secret Service within moments of shooting the former president.

One spectator, identified as firefighter Corey Comperatore, was killed, and two others were critically injured in the attack.