Trump assassination attempt raises questions about Secret Service's handling of security

As the FBI looked for a motive in Saturday's assassination attempt on former President Donald Trump by searching through the gunman's home and cell phone on Monday, multiple agencies are also searching for answers about how the gunman evaded detection even though he was spotted by members of the crowd.

Before a shot struck the former president, numerous witnesses in the crowd spotted the gunman laying on top of a nearby building.

"We're pointing at him, police are running around on the ground, and we're like 'hey man there's a guy on the roof with a rifle,'" witness Greg Smith said.

The map below shows just how close the gunman was able to get to the stage, less than 150 yards away.

Securing a site is a team effort between the Secret Service and local law enforcement.

The building where the gunman was perched was just outside the perimeter, and multiple sources told Eyewitness News that local law enforcement were in charge of that area. It was the staging area for the local police tactical team.

Retired Senior Secret Service Agent Donald Mihalek urges people not to jump to conclusions as the facts are still trickling in.

He says, snipers work in teams of two, and they're trained to take out a threat once the threat is confirmed.

"It looks to me they spotted the threat, took the shot just before or simultaneously as the shooter was shooting," Mihalek said.

What happened before, agencies are still working to find out.

Local police confirmed they were in the process of looking for suspicious activity outside the perimeter before the president took to the podium.

"I am aware that law enforcement has responded to a number of reports of suspicious activity," Pennsylvania State Police Lt. Col. George Bivens said.

But what steps local police took in an attempt to detain him and to secure the building remains to be seen.

"The question of course is where was the failure? How did the failure occur? What can the security service do moving forward to make sure the failure doesn't happen again?" Mihalek said.

Secret Service protection has been increased for the former president. Plus, Independent candidate Robert Kennedy Jr., whose father and uncle were killed by assassins, will now be receiving protection as well.