The U.S. Secret Service expressed support Tuesday for local law enforcement partners amid criticism of security at a Pennsylvania political rally where a gunman tried to kill former President Donald Trump.

“We are deeply grateful to the officers who ran towards danger to locate the gunman and to all our local partners for their unwavering commitment,” the Secret Service said in its statement early Tuesday. “Any news suggesting the Secret Service is blaming local law enforcement for Saturday's incident is simply not true."

Secret Service officials have described what happened as a failure for the agency responsible for protecting U.S. leaders.

The security plan for Saturday’s rally put the Secret Service in charge of the immediate event area, while the rooftop used by the gunman about 150 yards from where Trump was speaking was the responsibility of local police.

Some people at the rally said they frantically yelled at police when they spotted the gunman on the roof of the nearby building. Video from the site indicates such warnings came more than a minute before the shooter started firing toward Trump.

U.S. Homeland Security Secretary Alejandro Mayorkas, whose agency includes the Secret Service, told reporters Monday that he expected an independent investigation into the incident to begin within days.

Mayorkas said the probe would examine the actions of the Secret Service and other law enforcement agencies “before, during and after the shooting to identify the immediate and longer term corrective actions required to ensure that the no fail mission of protecting national leaders is most effectively met.”

One bullet pierced Trump’s right ear, and blood streamed down his face as his Secret Service detail surrounded him and rushed him to safety. One spectator was killed, while two others were critically injured and are hospitalized. A Secret Service sniper killed the gunman, identified as 20-year-old Thomas Matthew Crooks.

Trump was not seriously injured in the attack but easily could have been killed. Delegates meeting Monday at the Republican National Convention in Milwaukee, Wisconsin, officially named Trump the party’s presidential nominee in the November 5 national election against his Democratic opponent, President Joe Biden.

Biden on Monday ordered Secret Service protection for Robert F. Kennedy Jr., an independent presidential candidate in the election who trails far behind both Trump and Biden in national polling. Kennedy’s uncle, President John F. Kennedy, was assassinated in 1963, and his father, Robert F. Kennedy, was killed as he campaigned for the presidency in 1968.

The Federal Bureau of Investigation, the country’s chief criminal investigative agency, said it is continuing to look for a motive behind Saturday’s shooting. The FBI said it is investigating the case as potential domestic terrorism but that the probe is still in its early stages.

The FBI said Monday its technical specialists successfully gained access to Crooks’ phone, and they continue to analyze his electronic devices. It said the search of Crooks’ residence and vehicle had been completed.

The investigative agency said it has conducted nearly 100 interviews of law enforcement personnel, rally attendees and other witnesses and that the interviews are continuing.

Some information for this story was provided by The Associated Press and Reuters.