The sloped roof where a would-be assassin took aim at former President Donald Trump during a campaign rally in western Pennsylvania wasn’t safe enough for snipers.

This is a reason for not posting someone there, U.S. Secret Service Director Kim Cheatle said in an interview with ABC News on Tuesday.

“That building, in particular, has a sloped roof at its highest point,” she said. “And so, you know, there’s a safety factor that would be considered there that we wouldn’t want to put somebody up on a sloped roof.”

“And so, you know, the decision was made to secure the building, from inside,” Cheatle added.

The comment comes three days after 20-year-old Thomas Crooks opened fire on a crowd in Butler, Pa., less than 15 minutes after Trump took the stage, striking him in the ear. Trump was wounded but has continued his schedule, arriving in Milwaukee, Wis., on Sunday for the Republican National Convention and appearing in the main arena Monday night.

Since then, authorities – namely the Secret Service – have faced tough questions about the apparent security lapses that allowed the gunman to scale the roof 147 yards from the stage at the Butler Farm Show Grounds.

Eyewitnesses can be seen on video shouting for police to intervene as they watched Crooks belly crawl into position. Law enforcement was also stationed inside the building.

In a separate report from NBC News, a local official said a Butler Township police officer was boosted to the roof of the building, where he grabbed onto a ledge and saw Crooks, who then turned his rifle toward the officer. Unable to grab his weapon or radio, the officer dropped eight feet to the ground, injuring his ankle.