The person shot and killed during the attempted assassination of Donald Trump had dived on his family to shield them from bullets.
Trump, 78, was holding a campaign rally in Butler, Pennsylvania when a gunman opened fire, hitting his right ear and streaking his face with blood.
Former fire chief Corey Comperatore, who was attending the rally with family was killed, while two other people were also wounded.
The gunman, named by the FBI as 20-year-old Thomas Matthew Crooks, was shot dead by law enforcement.
The firefighter died as he tried to protect his family from a hail of bullets, his family said.
"The PA Trump Rally claimed the life of my brother, Corey Comperatore. The hatred for one man took the life of the one man we loved the most," the victim's sister said in the post on Sunday.
Pennsylvania governor Josh Shapiro told reporters: “Corey died a hero. Corey dove on his family to protect them last night at this rally. Corey was the very best of us."
The volunteer firefighter was survived by a wife and two daughters.
Mr Shapiro added: "Corey was a firefighter. Corey went to church every Sunday. Corey loved his community and most especially Corey loves his family."
Speaking after the assassination attempt, Donald Trump said people must remain "defiant in the face of wickedness".
Writing on his Truth Social platform on Sunday, Mr Trump thanked well-wishers and said: "It was God alone who prevented the unthinkable from happening.
"We will fear not, but instead remain resilient in our faith and defiant in the face of wickedness."
US President Joe Biden appealed for the country to "unite as one nation" after the shooting and said he was ordering an independent security review of the lead-up to the attack.
Mr Biden delivered brief remarks from the White House on Sunday after receiving a briefing on the investigation in the Situation Room.
He said he has directed the probe to be "thorough and swift," and asked the country not to "make assumptions" about the perpetrator's motives or affiliations.
The US President said he planned to deliver extended remarks to the nation on Sunday evening in a prime-time address from the Oval Office.
