At 2:27 pm Eastern Time,[6]:82 as Reagan walked out of the hotel's T Street NW exit toward his waiting limousine, Hinckley waited within the crowd of admirers. While the Secret Service extensively screened those attending the president's speech, in a "colossal mistake" the agency allowed an unscreened group to stand within 15 feet of him, behind a rope line.[6]:80–81,225 Unexpectedly, Reagan passed right in front of Hinckley. Knowing he would never get a better chance,[6]:81 Hinckley fired a Röhm RG-14 .22 cal.[18] blue steel revolver six times in 1.7 seconds,[6]:82[15] missing the president with all six shots.[19][17] The first bullet hit White House Press Secretary James Brady in the head. The second hit District of Columbia police officer Thomas Delahanty in the back of his neck as he turned to protect Reagan.[6]:82[20][21][22][23] Hinckley now had a clear shot at the president,[6]:81 but the third overshot him and hit the window of a building across the street. As Special Agent In Charge Jerry Parr quickly pushed Reagan into the limousine, the fourth hit Secret Service agent Timothy McCarthy in the abdomen[20][21] as he spread his body over Reagan to make himself a target.[6]:81[10] The fifth hit the bullet-resistant glass of the window on the open side door of the limousine. The sixth and final bullet ricocheted off the armored side of the limousine and hit the president in his left underarm, grazing a rib and lodging in his lung, stopping nearly an inch from his heart.[24][10][13] Had Parr hesitated for a moment, the president would likely have been hit in the head.[6]:224
After the shooting, Alfred Antenucci, a Cleveland, Ohio, labor official who stood by Hinckley, was the first to respond.[17] He saw the gun and hit Hinckley in the head, pulling the shooter down to the ground.[25] Within two seconds agent Dennis McCarthy (no relation to agent Timothy McCarthy) dove onto the shooter as others threw him to the ground; intent on protecting Hinckley to avoid what happened to Lee Harvey Oswald,[6]:84 McCarthy had to "strike two citizens" to force them to release him.[17] Agent Robert Wanko took an Uzi from a briefcase to cover the President's evacuation and to deter a potential group attack.[26]
Sixteen minutes after the assassination attempt, the ATF found that the gun had been purchased at Rocky's Pawn Shop in Dallas, Texas.[27] It had been loaded with six "Devastator"-brand cartridges which contained small aluminum and lead azide explosive charges designed to explode on contact; the bullet that hit Brady likely exploded in his skull. On April 2, after learning that the others could explode at any time, volunteer doctors wearing bulletproof vests removed the bullet from Delahanty's neck.