A local police officer locked eyes with the gunman who nearly killed Donald Trump at a rally in July – but there’s no evidence a warning ever reached Trump’s Secret Service detail, according to a report released on Monday.

A US House of Representatives task force has published its preliminary findings into the near-miss assassination attempt, outlining a list of security failings.

The report from the panel – made up of seven Republicans and six Democrats – states the attempt was “preventable and should not have happened”.

The committee’s investigation is ongoing, and it is also looking into a second suspected attempt on Trump’s life at his Florida golf course in September.

The new House panel report is based on interviews and documents related to the events of 13 July.

At the rally in Butler, Pennsylvania, Thomas Matthew Crooks, 20, climbed on to the roof of a nearby industrial building, which was just outside the event’s main security perimeter.

From that vantage point, he eight fired shots. One nicked the Republican presidential candidate’s ear and one killed a rally attendee. Two others were injured.

Local police noticed Crooks more than an hour before the shooting. He was looking at sniper positions and examining the stage through a gun rangefinder.

At one point Crooks ran from officers who were on the lookout for him. He evaded police until he was later spotted on the roof.

A Butler Township police officer then hoisted himself up on the roof. He testified that he locked eyes with the gunman.

“I see Crooks facing downrange towards the stage, but his eyes are back at me as I’m coming up [onto the roof],” the police officer said.

“And I would say, like, his facial expressions was surprised. His eyes were very big, like, ‘what are you doing up here?'”

Crooks pointed his assault rifle at the officer, who slipped, fell to the ground and then started yelling into his radio: “He’s got a gun. He’s got a long gun.”

The report noted: “To date, the task force has not received any evidence to suggest that message reached the former President’s (Secret Service) detail prior to shots fired.”

Other findings, some of which have been previously outlined in testimony and other public reports, include:

• “Inadequate planning and coordination before the rally”, with a disorganised walk-through of the site
• That local sniper teams had a limited field of vision
• There was no unified security command post, and communication between the US Secret Service and Butler Township law enforcement was slow and fragmented
• That local police fired a shot at the gunman which “may have caused Crooks to stop firing”. However, it did not hit Crooks, who was killed by a single shot from a Secret Service sniper
• That a ladder found at the scene did not belong to the gunman but was used by officers to climb onto the roof after the shooting. Crooks had bought a ladder that morning but abandoned it about 50 miles (80km) from the site. He managed to get onto the roof by climbing on air conditioning units

In a statement, Republican House Speaker Mike Johnson called the security failures by Secret Service outlined in the report “shocking and inexcusable”.