Washington — Former President Donald Trump on Thursday recounted for the first time the assassination attempt at his rally in Pennsylvania and said he initially believed he was under attack but survived because of the "grace of almighty God."

"So many people have asked me what happened, 'tell us what happened please,' and therefore, I'll tell you exactly what happened, and you'll never hear it from me a second time, because it's actually too painful to tell,"  Trump told the crowd gathered for the final day of the Republican National Convention in a speech formally accepting the party's presidential nomination.

The former president said he began speaking "very strongly, powerfully and happily" while discussing his administration's efforts to curtail illegal immigration at the southern border, and began to turn to his right toward a chart displaying border crossings when he heard a "loud whizzing sound" and felt something hit him in the right ear.

Trump said he believed immediately that it was a bullet and, after feeling his ear with his hand, saw it was covered with blood.

"I immediately knew it was very serious, that we were under attack, and in one movement, proceeded to drop to the ground," he said.

As U.S. Secret Service agents rushed to the stage and surrounded him for protection, Trump said he felt "very safe, because I had God on my side."

"The amazing thing is that prior to the shot, if I had not moved my head at that very last instant, the assassin's bullet would have perfectly hit its mark, and I would not be here tonight. We would not be together," he said.

Trump then praised the crowd of supporters who attended the rally and said after the gunshots rang out, they did not flee for the exits, but instead pointed to the shooter. The former president told the audience that he believes many in attendance thought he was dead and did not want to leave him.

"I'm not supposed to be here tonight," he said. "I stand before you in this arena only by the grace of almighty God. And watching the reports over the last few days, Many people say it was a providential moment. Probably was."

Trump then described lifting his right arm and shouting "fight," a scene that was captured by photographers at the rally and prompted cheers from the crowd.

"For the rest of my life, I will be grateful for the love shown by that giant audience of patriots that stood bravely on that fateful evening in Pennsylvania," he said.

Trump went on to pay homage to Corey Comperatore, who was killed in the shooting, and David Dutch and James Copenhaver, who were injured. The former president said he spoke to the families of the three men, and the crowd observed a moment of silence to honor Comperatore.

"There is no greater love than to lay down one's life for others," he said. "This is the spirit that forged America in her darkest hours, and this is the love that will lead America back to the summit of human achievement and greatness. This is what we need."

Trump said in the face of the attack, Republicans remain determined to deliver a government that serves the American people.

"Nothing will stop me in this mission because our vision is righteous and our cause is pure," he said.

Trump's speech closing out the Republican National Convention is the first he has given in the wake of the assassination attempt at Saturday's rally in Butler. The gunman, identified by the FBI as 20-year-old Thomas Matthew Crooks, was shot and killed by a Secret Service sniper.

The former president suffered an injury to his ear when it was grazed by the bullet and has since been wearing a white bandage over it. In a show of support for Trump, a number of convention attendees have also placed fake bandages over their ears.

Trump returned to his property in New Jersey after the shooting, but flew to Milwaukee on Sunday for the convention. He has attended all four nights and listened to speeches from Republican lawmakers, governors, his former presidential primary opponents, family members and his newly minted running mate, Sen. JD Vance of Ohio.

In the wake of the attack, Trump called for unity and told the Washington Examiner that he re-wrote his speech accepting the Republican presidential nomination. A senior adviser for his campaign, Danielle Alvarez, told CBS News that the address is "deeply personal" and "heartfelt."

"This speech, he wrote personally," she said. "He was making final edits up until just the walkthroughs and the rehearsals today. And it will be very personal. It will be from the heart. And it will meet the moment. It will call for the unity that the nation needs."

Melissa Quinn

Melissa Quinn is a politics reporter for CBSNews.com. She has written for outlets including the Washington Examiner, Daily Signal and Alexandria Times. Melissa covers U.S. politics, with a focus on the Supreme Court and federal courts.

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