In the aftermath of what appears to be an assassination attempt, former President Donald Trump called for unity and resilience on Sunday as shocked leaders retreated from the political divide following the shooting that left him injured but "fine."

A former fire chief who was attending the rally with his family was killed, as well as the shooter. Two other people were also injured.

The presumptive Republican presidential candidate said the top of his right ear was perforated by gunfire. His aides said he is in "high spirits" and in good health.

He wrote on his social media: "I immediately knew something was wrong when I heard the buzzing and gunshots, and I felt the bullet penetrate the skin right away." "There was a lot of bleeding."

In a later social media post on Sunday, Trump said: "Only God prevented the unimaginable from happening."

He added: "At this moment, it is more important than ever that we stand united, show our true character as Americans, and remain strong and determined, not allowing evil to prevail."

Pennsylvania Governor Josh Shapiro identified the individuals who were killed on Sunday as Corey Compiratori, a former fire chief from the area, and stated that he "died a hero."

Shapiro said: "His wife told me he was shielding his family to protect them." The governor declined to discuss the condition of the other two injured individuals.

The FBI identified the shooter as Thomas Matthew Crooks, 20, from Bethel Park, Pennsylvania, located about 50 miles from the site of the shooting. An FBI official stated that investigators have not yet determined a motive.

Secret Service agents shot Crooks fatally. The agency said the shooter attacked from an elevated position outside the gathering at a farm show in Butler.

Authorities said one attendee was killed and two bystanders were seriously injured. All were identified as men.

Law enforcement officials told the Associated Press that bomb-making materials were found inside the vehicle of the suspect in the shooting at the Trump gathering. Bomb-making materials were also found at his home. Officials were not allowed to discuss details of the investigation publicly and spoke to the Associated Press on condition of anonymity.

Law enforcement officials said investigators believe the weapon used by Crooks was purchased by his father at least six months ago. Federal agents are still working to understand when and how the son obtained the firearm and gather additional information about Crooks, according to the officials.

Crooks' political inclinations were not immediately clear. Records show that Crooks was registered as a Republican voter in Pennsylvania, but federal campaign finance reports also indicate that he donated $15 to the Progressive Political Action Committee on January 20, 2021, the day President Joe Biden was inaugurated.

Authorities told reporters that Crooks was not carrying identification, so they were using DNA and other methods to verify his identity. Law enforcement found an AR-type rifle at the scene, according to a person familiar with the matter who spoke on condition of anonymity to discuss the investigation.