Cellphone and detonator found on rooftop near suspected Trump shooter

A picture obtained by a Pittsburgh-area TV station showed a cellphone and detonator carried by the gunman who attempted to assassinate Donald Trump at the Butler county show grounds in western Pennsylvania last Saturday.

Related: Pennsylvania town aims for normality as police feel heat over Trump shooting

The items were shown on the rooftop from which Thomas Matthew Crooks used an AR-15-style rifle to fire on the former president and Republican presidential nominee.

Trump suffered an injury to his right ear. One rally-goer was killed and two injured.

The 20-year-old gunman was shot dead by security officers.

In a febrile and partisan national atmosphere, the shooting appears to have boosted Trump’s image in his campaign against Joe Biden.

The Democratic president has called for a cooling of political invective. At the Republican national convention in Milwaukee, Trump has worn a prominent bandage on his ear as speakers have celebrated his narrow escape.

WPXI, an NBC-affiliate station, obtained and reported the picture of Crooks’s phone and detonator on Tuesday.

The gunman’s motives remained unclear, though officials said they had been able to access his phone. Sources told the Washington Post that “cracking the phone did not crack the case”, though it offered leads to pursue.

Crooks’s car was found to contain a metal box of explosives connected to a receiver, CNN reported , adding that investigators were considering the idea Crooks intended to create a distraction during the shooting.

WPXI also reported on continuing confusion over why the gunman was not confronted before he fired on Trump.

Crooks was seen by witnesses and by law enforcement but not conclusively confronted.

Kimberly Cheatle, the director of the US Secret Service, has said local police officers were inside the building from which Crooks shot.

“We did share support for that particular site and the Secret Service was responsible for the inner perimeter,” Cheatle told ABC News. “And then we sought assistance from our local counterparts for the outer perimeter.

“There was local police in that building – there was local police in the area that were responsible for the outer perimeter of the building.”

WPXI reported that that local police were never stationed in the building concerned.

Tom Knight, the Butler township manager, said: “So the building was outside the event area and there was conversations about the logistical coverage for the building, what the building had for access points and what access points could be controlled.”

WPXI said sources said Crooks was still on the ground when Trump began speaking.

Kinght said there was then “a radio transmission indicating that there was a suspicious individual on the rooftop, [and it] was my understanding [that] was our officers’ first notification to begin moving towards that building.

“Two of the officers went to what appeared to be the lowest point from ground to roof. One of the officers actually boosted the second officer up high enough for him to grab hold of the roof. He did in fact see an individual on the roof with a weapon.”

Crooks pointed his rifle at the officer, Knight said, as the officer hung on to the roof with both hands, unable to reach his radio or his own weapon.

The officer “lost his own grip and fell approximately eight feet to the ground”.

Shortly after that, Crooks opened fire.