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A bipartisan panel condemned the Secret Service handling of former President Trump's rally in Butler, Pennsylvania on Thursday, saying the agency needs "fundamental" changes to be effective.

The panel, made up of former senior law enforcement and government officials, warned that if there are not extensive reforms at the Secret Service, then "another Butler can and will happen again."

Butler, Pennsylvania, was the site of the first assassination attempt against Trump this year. The Secret Service faced heavy criticism for negligence and sluggish reaction speed.

"The Secret Service as an agency requires fundamental reform to carry out its mission," the panel wrote in a letter to Homeland Security Secretary Alejandro Mayorkas. "Without that reform, the Independent Review Panel believes another Butler can and will happen again."

COPS NAB MAN ALLEGEDLY CARRYING ILLEGAL GUNS NEAR TRUMP'S COACHELLA RALLY; SUSPECT SAYS HE BACKS EX-PRESIDENT

Donald Trump is surround by U.S. Secret Service agents at a campaign rally,

An independent review panel says the Secret Service needs extensive reforms in order to be effective. (AP Photo/Evan Vucci)

The panel's review highlighted key issues both within the Secret Service and specifically regarding the July 13 assassination attempt. The agency had poor communications both internally and with local law enforcement, the panel said. Agents on the ground also had no plan to secure key buildings around the rally venue.

"The failure to secure a complex of buildings, portions of which were within approximately 130 yards of the protectee and containing numerous positions carrying high-angle line of sight risk, represents a critical security failure," the report said.

"Relying on a general understanding that ‘the locals have that area covered’ is simply not good enough and, in fact, at Butler this attitude contributed to the security failure," it continued.

An aerial image shows investigators surveying the area of the attempted assassination of former President Donald Trump

An independent panel says the Secret Service failed to ensure the complex of buildings near Trump's rally in Butler was secure. (Fox Flight Team )

The panel also noted a breakdown in communications. There were two command posts at the Butler rally, one for local law enforcement and another for the Secret Service.

Secret Service agents also had to switch radio channels due to an event for First Lady Jill Biden in Pittsburgh. The first lady's Secret Service team's communications could be heard at the Butler rally at the time.

New drone footage shows sight line Trump shooter used to open fire on rally

Drone footage shows the sight line the Trump shooter used to open fire at the rally in Butler, Pennsylvania. (Fox News)

The panel ultimately recommended that the Secret Service bring in outside leadership, as well as de-emphasize its role in investigating financial crimes.

"In the Panel’s opinion, it is simply unacceptable for the Service to have anything less than a paramount focus on its protective mission, particularly while that protective mission function is presently suboptimal," the report said.

Acting Secret Service Director Ronald Rowe respond to the report in a Thursday statement.

"We respect the work of the Independent Review Panel and will carefully examine the report and recommendations released today," Rowe said. "However, we are not waiting to act. We have already significantly improved our readiness, operational and organizational communications and implemented enhanced protective operations for the former president and other protectees."

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The panel members were Mark Filip, deputy attorney general under President George W. Bush; David Mitchell, who served in numerous state and local law enforcement roles in Maryland and Delaware; Janet Napolitano, homeland security secretary under President Barack Obama; and Frances Fragos Townsend, Bush's assistant for homeland security and counterterrorism.

Read the full independent panel report below. On mobile? Click here

The Associated Press contributed to this report.