According to an investigation, a police sniper may have saved lives by taking down Donald Trump's would-be assassin with a shot to the rifle.

Thomas Matthew Crooks took his initial shots in Butler, Pennsylvania, and the sniper's bullet broke his pistol and confused his aim, according to a report by Congressman Clay Higgins of Louisiana. He was slain by a Secret Service sniper shortly after.

According to US media, the Secret Service has temporarily transferred some of President Joe Biden's bodyguards to President Trump.

Trump will also be given bulletproof glass protection to allow him to resume outdoor rallies.

The former president did not have the protection during his 13 July rally in Butler when a bullet nearly hit him squarely in the head.

Mr Higgins' report said a Butler SWAT operator was the first to fire at Trump's assassin - from 100 yards away.

The congressman said the sniper "ran towards the threat, running to a clear shot position directly into the line of fire".

Then, in a single shot, he fired at the gunman and hit part of his rifle, the report said.

This knocked the gunman off his position temporarily, but, "after just a few seconds", he "popped back up" before he was fatally shot by a Secret Service sharpshooter.

Crooks killed one crowd member and critically injured two others in the attack.

Security levels around the former president have increased since then.

New records obtained by ABC News detail internal discussions by local authorities about security planned the day of the assassination attempt, with the Butler County sheriff noting the "circus" and large crowds the rally would bring. The records also include text messages showing frustration by local authorities after the shooting.

Local authorities discussed the Secret Service requesting a sniper and overwatch support, along with counterassault teams and a quick reaction force.

In an email obtained by ABC News to Butler County's district attorney, Sgt. Edward Lenz of the Adams Township Police Department details that they planned to provide two snipers, a quick reaction force and two mobile counterassault teams.

The counterassault teams "would respond to and address an attack directed at the presidential candidate inside of the venue, whether it be a coordinated attack with multiple assailants, or a single attacker", he wrote.

He said the quick reaction force would respond to any "high-risk incidents occurring outside of the venue".

The records came after the transfer of Secret Service agents amid threats against Trump, 78. The move was made possible due to the reduced travel schedule of Mr Biden after he dropped out of the election race, according to a report in The New York Times.

The reassigned officers were responsible for either travelling with Mr Biden, or going in advance of him to set up security measures at an event, a source told the newspaper.

Kimberly Cheatle, the director of the Secret Service, resigned on 23 July following a hearing at the US House of Representatives about the assassination attempt.

Politicians on the House Oversight Committee criticised the lack of information in her answers to their questions regarding security planning and how officers responded to reports of the gunman’s suspicious behaviour prior to the shooting.

Gunman Thomas Matthew Crooks, 20, was shot and killed by a Secret Service counter-sniper team after he fired eight bullets in Mr Trump’s direction from a rooftop just outside the rally's security perimeter.

The FBI is currently investigating the protection failure and political leaders in the US Congress have also started inquiries.