Comer opens the hearing by calling 13 July a "horrifying moment in American history" and says the bullets was "less than an inch from taking" Trump's life.

He praises the "the bravery of the crowd, unwavering in its refusal to panic" and the "bravery of Trump for refusing to run".

While he acknowledges and thanks the bravery of the Secret Service agents there that day, he says the tragedy was "preventable" and accuses the agency of a "history of incompetence".

He repeats that he thinks Cheatle should resign. The Secret Service head has already refused to do so and is appearing at the hearing today after being compelled to by subpoena.

Bernd Debusmann Jr
Reporting from Capitol Hill

We're now underway, with committee chairman James Comer telling the room that the hearing is "for the American people" and going through the events of 13 July in Butler.

"It was a horrifying moment in American history," he says.

While Comer is thanking the "individual" Secret Service agents who were there, he has quickly shifted the blame on the wider service and its failure to stop a "preventable" incident.

Kimberly Cheatle is now in the room, sitting by herself at a long table in the middle of the room as Comer recounts the agency's failure to live up to its "zero-fail" mission.

"We are concerned the Secret Service lacks the proper management to keep the president safe from bad actors," he adds. "Americans want answers".

The hearing has just begun, and we'll soon be hearing Cheatle's opening statement.

Stay with us for more - and you can follow every moment by hitting watch live above.

Bernd Debusmann Jr
Reporting from Capitol Hill

Image source, EPA

We just caught our first glimpse of Secret Service Director Kimberly Cheatle, who entered the room for a few seconds, took a glance at the table where she will be sitting and then quickly walked past picture-snapping photographers to a back door in the rear of the room.

As she walked by, she passed a number of lawmakers – none of whom seemed to acknowledge her presence.

The hearing room is starting to fill out a bit now. Among those who are currently in the room is House Speaker Mike Johnson, who is in the back of the room shaking hands with Republican lawmakers, including South Carolina's Nancy Mace and Arizona's Andy Biggs.

Just to my left, Florida Republican Anna Paulina Luna is exchanging friendly banter with her seat neighbours, South Carolina's Russell Fry and New York's Nick Langworthy.

Image source, Getty Images

The hearing with Secret Service Director Kimberly Cheatle will be getting under way in the next few moments.

We'll be bringing you updates throughout, but you can also watch it by clicking "Watch live" on the stream at the top of this page.

Bernd Debusmann Jr
Reporting from the hearing

There's an air of excitement here at the Rayburn House Office Building on Capitol Hill, where US Secret Service Director Kimberly Cheatle is expected to arrive soon.

Hours before the hearing there were several dozen people already queuing up along the wall of a drab, white, brightly lit hallway.

Most of those coming in are hill staffers, or curious members of the public. Many are students, here in Washington for summer programmes or internships with lawmakers.

But there are a few other faces I recognize.

One of them Micki Witthoeft, the mother of Ashli Babbitt, a 35-year-old Air Force veteran who was shot and killed by police during the 6 January Capitol riot.

In her upcoming remarks, Cheatle is expected to take responsibility for what took place at the shooting in Butler, Pennsylvania - although what she says may be limited by the fact that there are multiple ongoing investigations into the shooting.

Stay with us for more updates.

Bernd Debusmann Jr
Reporting from Capitol Hill

Through today’s hearing, lawmakers on the House committee for oversight and accountability hope to understand the Secret Service’s "management of resources and personnel” ahead of and during the rally in Butler. Its ultimate aim is to understand what exactly went wrong.

Republicans on the committee have also called on the Secret Service to produce evidence including internal communications, audio and video recordings, messages to local law enforcement, maps, diagrams and pre-event assessments. Among the main questions that are likely to be asked are:

• Why was the rooftop which Thomas Matthew Crooks shot from not secure?
• Who was responsible for securing the building?
• Why was Trump was allowed on stage despite concerns that the suspect had been seen with a rangefinder?
• Was there any breakdown in communication between the USSS and local police?
• Was the event adequately resourced?
• Did the USSS react properly once the suspect began shooting?

Donald Trump was speaking at a campaign event in the city of Butler, Pennsylvania on 13 July when a gunman opened fire.

Here's a breakdown of how that all unfolded. All times are local:

17:00: Trump was scheduled to start addressing the crowd

18:03: He takes the stage to Lee Greenwood’s“God Bless the USA”

18:11: A few minutes into his campaign speech, loud shots ring out

18:12: Secret Service agents swarm the former president before he is rushed off stage with blood near his ear and on the side of his face

18:14: Trump's motorcade leaves the rally

18:42: Secret Service issues a statement, confirming that Trump is safe and there is an active investigation into the incident

19:03: Trump’s campaign says he's “fine”

19:45: Law enforcement confirms that the suspect is dead, along with an audience member

20:13: Biden condemns the attack and says during a briefing that he is trying to speak with Trump over the phone as soon as possible

20:42: Trump shares his first account of what happened, saying a bullet pierced his upper part of his right ear

21:33: The FBI Pittsburgh says it is the lead federal law enforcement agency in the investigation

Image source, Getty Images

The embattled director of the US Secret Service, Kimberly Cheatle, has nearly three decades of experience in the agency.

She first joined the Secret Service in 1995. During her time as an agent, Cheatle she was involved in evacuating then-Vice-President Dick Cheney from the White House – which many feared was in danger –during the 11 September, 2001 attacks.

She later went on to become supervisor of Joe Biden’s protective detail when he was vice-president, before becoming the deputy assistant director of protective operations.

Cheatle was the first woman to serve in that role, which oversees the safeguarding of the President and other VIPs.

After a short stint in the private sector working for PepsiCo, Cheatle was appointed to her current post of director by President Joe Biden in 2022.

Cheatle has spoken of the challenges of being a woman in an agency in which there relatively few of them –especially in leadership positions.

“That achievement in a male-dominated industry was not lost on me,” she told Security Magazine in 2022.

“I kept a photo on my desk of the first five women sworn into the service, and I used that to remind me that these women created opportunities for me and I can help others grow and lead as well.”

Bernd Debusmann Jr
Reporting from Capitol Hill

Image source, Getty Images

Established in 1865, the Secret Service is one of the oldest law enforcement agencies in the US.

While the service also investigates financial and counterfeiting crimes and guards diplomatic missions in Washington DC, it is most famous for providing protective services to the president, vice-president and their families.

Secret Service agents clad in dark suits, sunglasses and earpieces are a constant presence for current and former first families.

The agency is also authorised to protect visiting foreign heads of states and other prominent dignitaries, as well as major presidential candidates and their spouses within 120 days of a general election.

These protective duties require careful planning and coordination with local and state law enforcement agencies.

Planning the security for major presidential or campaign events typically begins with the deployment of an advance team to scout out the area and meet with the protectee’s staff.

During this visit, agents will look to identify any potential security vulnerabilities and designate areas of responsibility for the Secret Service and other law enforcement partners.

While the Secret Service is responsible for the inner-most cordon around the so-called “principle” - in this case, Donald Trump - local police are generally responsible for the outer rings of security in situations like the campaign rally in Pennsylvania.

Secret Service Director Kimberly Cheatle will soon appear before a House committee to face questions over security lapses at the rally where an assassination attempt was made on former US President Donald Trump’s life.

Investigators believe the gunman, 20-year-old Thomas Matthew Crooks, opened fire at Trump while he was addressing a crowd in Butler, Pennsylvania. One audience member was killed and three people, including Trump, were injured.

Lawmakers say the Secret Service identified the gunman as suspicious some 20 minutes before he opened fire.

Calls for Cheatle to step down have been mounting in the wake of the incident, with Republicans, who control the House, unified in pushing for her to go.

Cheatle will appear before the House oversite committee at 10:00 ET (15:00 BST).

We’ll be bringing you updates throughout here on this page, but you can also follow our live stream by pressing the "Watch live" button at the top of this page once it starts.