What went wrong? How did Secret Service allow shooter to get so close to Trump?

Investigations into the sniper shooting that injured Donald Trump and killed a local firefighter must focus on whether several key Secret Service protocols were violated, current and former law enforcement officials said Sunday.

Chief among them: Why wasn't a building well within 1,000 yards of the former president locked down enough to prevent the shooter from nearly assassinating the presumptive GOP presidential nominee?

In an exclusive interview, former Secret Service Director Julia Pierson told USA TODAY that maintaining such a sniper security perimeter is part of the agency's responsibility for safeguarding "protectees" like Trump from harm. Yet the man identified as the sniper, 20-year-old Thomas Matthew Crooks , fired off numerous rounds from a building top about 150 yards from Trump's lectern at Saturday's rally in Butler, Pennsylvania.

“I think 1,000 yards is the sniper capability that we have a concern about for the President. So anything that's within that range, that is a professional, makable shot... and you want to know about it,” Pierson said.

“When you think about it, it's a football field and a half … and that is a makeable shot by an individual.  And obviously an inch would have made a difference in this case and Trump wouldn't be with us,” said Pierson, who spent three decades with the Secret Service, much of that on presidential protective operations, before becoming director in 2013.

Crooks managed to fire off numerous rounds , injuring two other people in the crowd, before being killed by a Secret Service counter-sniper sharpshooter from another nearby roof. On Sunday evening, the FBI clarified that Crooks had used an "AR-style 556 rifle ."

Rep. Ruben Gallego, a former Marine and Arizona Democrat, said that those "responsible for the planning, approving and executing of this clearly insufficient security plan need to testify before Congress and be held accountable."

"There should never have been a clear line of sight on the former president. My Marine Corps training taught me that,” said Gallego, an Iraq veteran who is running for Senate in Arizona.

President Joe Biden also weighed in, directing Secret Service Director Kimberly Cheatle to review all security measures for the Republican National Convention, which begins Monday in Milwaukee. He said he had ordered an independent review of the security measures taken at the Trump rally to "assess exactly what happened."

First assassination attempt against a former or current President in 43 years

The shooting marks the first assassination attempt against a former or current U.S. president since President Ronald Reagan was injured in a March 1981 shooting at a Washington, D.C. hotel. Before that, in 1975 a member of the Manson Family cult tried to shoot President Gerald Ford at close range in Sacramento, California but failed to chamber a round into the gun.

The Secret Service has confirmed that it is investigating how a gunman armed with an AR-style rifle was able to get close enough to shoot and injure Trump in what appears to be an epic failure of one the agency's primary duties of protecting VIPs. The FBI, state police and the U.S. Congress also will be seeking to answer the many swirling questions.

Some of those questions: How did Donald Trump’s would-be assassin gain a high-ground vantage point to fire off a potentially fatal head shot against the former president? Why didn’t Secret Service counter-sniper teams neutralize Crooks before he got off so many rounds from his high-powered rifle, killing one Trump rally-goer and injuring two others?

Also, if Crooks had been flagged by local authorities for acting suspiciously as some media have reported, why was he then able to climb atop a nearby building with a rifle, firing a shot that grazed Trump's ear? And why did Secret Service agents allow Trump to stand back up defiantly and do three fist-pumps when it wasn't clear that the threat had been fully neutralized?

Could this have been stopped before it started?

John Miller, a former senior FBI and New York Police Department official, said on CNN that Crooks had been observed acting suspiciously near the magnetometers, or metal detectors stationed outside the event by local law enforcement agencies.

Those officials then shared those concerns with the Secret Service and other authorities “and people had his description and were looking around for him,” said Miller, who’s currently a CNN analyst.

At some point, Miller said, Crooks “left the magnetometer area. And then at some point, people start to point out there's a guy who's climbing on that roof, and he has a rifle and police are putting that over the radio.”

According to some video and media reports, the Secret Service counter-sniper on a nearby rooftop was aiming at the shooter, perhaps before he took some or all of his shots.

“The counter sniper appears to be looking through his scope as if he's scanning for something. … And then, when the shots are fired, takes out the shooter from his position almost immediately,” said Miller, the NYPD’s deputy commissioner of Intelligence & Counterterrorism until 2022. “So we have to fill in those gaps. What happened during those seconds? What were the communications? What did he see through the scope, and did he act at his first opportunity? And we'll learn that later.”

Miller said the counter-sniper succeeded in eliminating the threat quickly. “That part worked,” he said. But, he added, “What about the front end? Could this have been stopped with faster or more clear communications or a more intense search?”

Investigations have already begun

It’s possible and even likely that the Secret Service security plan for the rally, in conjunction with local and state authorities, took into consideration the building from which Crooks allegedly sprayed bullets. It could have been locked down from the inside, prompting Crooks to have to climb to the roof from the outside as part of the security plan put in place by authorities before the rally.

But the entire sequence of events will be investigated to find out what went so wrong that Crooks was able to gain access to the roof of the building, including whether he might have surveilled the site ahead of time to find the best way up, according to current and former law enforcement officials.

William Pickle, a former special agent in charge of the Secret Service's Vice Presidential Protective Division who oversaw Vice President Al Gore’s detail, said there are provisions in any Secret Service security survey that nearby buildings are accounted for. The Secret Service regularly secures public areas such as parade routes peppered with large buildings, and advance teams interview building owners and business managers to determine who has access to the building and at what times to determine if agents need to stand watch.

“We know who’s there, why they’re there, we have control over those buildings,” Pickle said. “It seems like somewhere in this security survey, someone dropped the ball on those particular buildings.”

Though Pickle said the counter-sniper that took out the shooter did an “outstanding” job, he questioned if the Secret Service had posted additional counter-sniper teams to sufficiently cover the entire event perimeter. “A gunshot knows no boundaries except by the velocity and distance a bullet can travel,” Pickle said. “This was a relatively easy shot, and Donald Trump may have been the luckiest man in the world yesterday. He survived by about half an inch."

Secret Service spokesman Anthony Guglielmi told USA TODAY on Sunday that he was traveling to Milwaukee, the site of the upcoming Republican National Convention, and would not be in a position to talk until later in the day. At 2 p.m., he said he was still "unable to respond" to claims that the Secret Service made mistakes in allowing the shooter to gain such a close vantage point.

Three hours later, another senior Secret Service official also declined to comment on whether the agency failed in its mission to protect Trump at the Saturday rally.

“Any questions regarding yesterday’s event can be directed to our public affairs office out of DC,” said Audrey Gibson-Cicchino, the agency’s coordinator for the upcoming Republican National Convention in Milwaukee. Speaking at a news conference there, she said she could only discuss convention security measures.

In a news conference early Sunday morning, the FBI special agent in charge of the Pittsburgh field office, Kevin Rojek, had confirmed that the FBI is leading the investigation into the shooting and that it “is our assessment at this time” that law enforcement did not know the shooter was on the roof until he began firing.

“It is surprising,” Rojek said when asked about the gunman’s close vicinity to the rally. He said that proximity is among the details that will be a focus of the investigation. Rojek added: “The Secret Service really needs to answer that question. They conduct the initial site survey.”

At the midnight news conference, State Police Lt. Col. George Bivens had deferred questions about whether there was anything about the venue that made it particularly difficult to secure by the Secret Service, which did not have representatives at the televised briefing.

Bivens also said he would not speculate on “how close a call” it was for Trump.

But Bivens confirmed that law enforcement is following up on a “number of suspicious occurrences” including accounts from witnesses who said they tried to flag police about the activity of a person outside the rally moments before the shooting.

Calls for answers from both sides of the aisle

Sen. James Comer, a Kentucky Republican who chairs the House Oversight committee, was one of several lawmakers who called for an immediate investigation into potential lapses by the Secret Service.

Comer said in a statement that he has already contacted the Service Service for a briefing and he called on Cheatle – the director – to testify about what went wrong. His committee will send a formal invitation soon, Comer said.

"Political violence in all forms is unamerican and unacceptable," Comer said in his statement. "There are many questions and Americans demand answers."

Pennsylvania Sen. John Fetterman, a Democrat, also called morning for an urgent investigation to explain what happened. Several hours later, however, Pennsylvania Gov. Josh Shapiro, also a Democrat, sidestepped a question at his own news conference about potential Secret Service failures in preventing the shooter from climbing atop the building.

"I'm not getting into ... any questions regarding the ongoing investigation," Shapiro said. "I trust that the FBI and the Pennsylvania State Police will keep you posted throughout the day and in the days ahead as to their investigations."

Contributing: Melissa Brown, a state political reporter at The Tennessean in Nashville, Tennessee.

This article originally appeared on USA TODAY: What went wrong? How did Secret Service allow shooter to get so close to Trump?