The Department of Homeland Security's inspector general's office said Wednesday that it will investigate the Secret Service effort to provide security at Donald Trump's campaign rally in Pennsylvania where the former president was shot and a rallygoer killed.

A notice posted on the office's "ongoing projects" web page for counterterrorism and homeland threats said the goal is to "evaluate the United States Secret Service's process for securing former President Trump's July 13, 2024 campaign event." The Secret Service falls under Homeland Security.

Also Wednesday, House Speaker Mike Johnson announced a bipartisan task force within the House to investigate the assassination attempt, saying "we need answers for these shocking security failures."

President Joe Biden previously ordered an "independent review" of the security measures at the event. Secret Service Director Kimberly Cheatle called the shooting "unacceptable" but said she will not resign.

Trump was speaking before throngs of supporters at the Butler Farm Show grounds when a gunman opened fire from the roof of a nearby building. Trump, his face bloodied from a bullet that apparently injured his ear, was hustled off the stage by Secret Service personnel. A Trump supporter was killed and two others were critically wounded before a sniper fatally shot the gunman.

The Secret Service has drawn criticism for failing to keep the shooter from gaining access to the roof, 150 yards from the rally, with an AR-15 semiautomatic rifle. Local police officers had been stationed inside the building but none on the roof.

A hero, firefighter, Trump supporter:What will Corey Comperatore's death mean?

Developments:

∎ The father of the gunman called police after the shooting, worried that his son and a gun were missing, three senior law enforcement officials told NBC News. Fox News is reporting that the family called authorites before the shooting took place.

Iran denies plotting to kill Trump

Iran rejected "malicious" reports of an alleged plot to assassinate Trump, saying the Islamic nation seeks a "legal path to bring him to justice" for ordering the assassination of an Iranian general in 2020.

The White House confirmed to USA TODAY a report that Trump's security was increased in recent weeks after intelligence showed Iran had been plotting to kill him. National Security Council spokesperson Adrienne Watson, in a statement issued Tuesday, said Iran has sought revenge since Trump ordered the killing of Qassem Soleimani, who Trump later described as “the number-one terrorist anywhere in the world.”

Iran Foreign Ministry spokesperson Nasser Kanaani “strongly rejects any involvement in the recent armed attack against Trump or claims about Iran’s intention for such an action, considering such allegations to have malicious political motives and objectives.”

Iran's mission to the U.N. said in a statement that Trump remains a criminal who must be prosecuted and punished in a court of law for ordering Soleimani's assassination.

"Iran has chosen the legal path to bring him to justice," the statement said.

Who was Trump shooter Thomas Matthew Crooks?

Thomas Matthew Crooks wasn’t an ex-CIA agent with a homemade gun that could slip through metal detectors. He didn’t carry an Uzi and wear a black tuxedo. He was not a professional killer like the ones depicted in those movies. Crooks was an isolated Gen-Z'er with an associate’s degree who worked a low-wage job and lived with his parents. Yet in an increasingly online world, where digital surveillance is easier than ever, the 20-year-old managed to stay unusually hidden while devising a plan to murder a former U.S. president – nearly successfully – in just 10 days of planning. Read more here.

“The security failures by law enforcement that day helped him look a lot more sophisticated than he would normally,” said Seamus Hughes, a researcher at the National Counterterrorism Innovation, Technology and Education Center at the University of Nebraska Omaha. “If you had put an agent on the roof as opposed to in the building, it goes from a very sophisticated attack to a very foolish attack.”

− Kenny Jacoby, Kristine Phillips and Christopher Cann

Trump's would-be assassin:Had little time to prepare – and left little trace of plot

Friends, family to honor shooting victim Corey Comperatore

Friends and family of Corey Comperatore will gather Thursday in Freeport, a small town on the Allegheny River, to pay their respects to the only person killed at Saturday's tragic campaign rally. Funeral services will be held on Friday at his longtime Butler County church. Comperatore has been proclaimed a hero after Gov. Josh Shapiro said the former volunteer firefighter dived onto his family to protect them when the shooting started.

James Sweetland, a doctor from Dubois, Pennsylvania, who was at the rally, rushed to help Comperatore. But he had suffered a shot to the head above his ear and never regained consciousness. 

"Yesterday time stopped," Allyson Comperatore, his daughter, said on Facebook. "And when it started again my family and I started living a real-life nightmare." Read more here.

− Chris Kenning

Contributing: Tom Vanden Brook