BETHEL PARK, Pa. – Days after a would-be assassin killed a bystander and wounded two others while trying to kill former President Donald Trump, questions remain about how an armed man was able to climb onto a rooftop less than 150 yards from a major political candidate with a rifle and a clear line of sight.

The modern Secret Service is “stretched too thin” with new responsibilities and protectees, while its budget and manpower haven’t caught up with the times, according to a former agent and security consultant who said there were missed chances in the past two decades that left his former agency overworked.

“They got a real opportunity after 9/11 to ask for increased funding, double the size of the agency, really increase the capabilities, and none of the directors did that,” said Bill Gage, an expert on active shooter response who retired from the Secret Service after 13 years with the agency, including 6 ½ as a member of the counter assault team.

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“In a perfect world, you have 30 CS teams and 500 agents,” he said, using the agency’s acronym for the counter-sniper team that took out the assassin. “But the Service just doesn’t have those resources.”

Even a third of that manpower would have been sufficient, he said.

Instead, videos from the rally show just a single CS team returning fire and neutralizing the suspect as a group of agents on the ground swarmed the former president, shielding him with their bodies.

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Additional agents in tactical gear were pictured over the suspect’s corpse on the rooftop moments later.

The Service’s duties have expanded, and the country is also in an active stretch of the busy 2024 campaign season, where President Biden and his predecessor and challenger, Trump, are both on the road regularly; the Republican National Conference is set to kick off in Milwaukee – and Chicago will host the Democratic National Conference in a few more weeks.

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“When I first joined the service in 2002, we were only protecting the president, the vice president and a few members of their family,” Gage told Fox News Digital. “By the time I left, we were protecting the vice president’s grandkids, foreign presidents, former presidents who were taking trips overseas.”

As the list of protectees expanded, so did the list of threats. The Islamic State terror group rose alongside Al-Qaeda. Fears grew about home-grown terrorism. But the Service saw no significant growth in budget or personnel, Gage said.

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The U.S. Secret Service has also faced questions over its preparedness and a number of scandals in recent years.

The agency took more heat this week after a would-be assassin climbed on top of a building outside the secure perimeter of a Trump rally in Pennsylvania. The suspect, Thomas Matthew Crooks, 20, died at the scene after a Secret Service counter-sniper team returned fire.

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But not before he fatally struck a 50-year-old engineer named Corey Comperatore, a father of two.

He also wounded two other spectators – and Trump was seen with blood on the side of his head after he said a bullet punctured his right earlobe.

Crooks climbed up on top of a building across from the rally with an AR-15-style rifle.

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Authorities have been criticized for a delayed response after witnesses spotted the armed Crooks on the roof and began to shout for help.

But Gage and other experts argue that the agents on scene were likely already responding amid the chaos.

“I think these people are probably being honest and sincere, but to say that nothing was being done, you know, until we can get transcripts of the radio traffic, I think that’s just wild speculation,” he said.

Still, he said, with more planning and resources, the attack could’ve been thwarted earlier.

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“I love the Secret Service, but it’s not without fault,” he said. “And I think there was some fault here. Both in the planning and the resources that were devoted to this.”