Sen. Bill Frist, R-Tenn., a Harvard-trained heart surgeon, had just finished presiding over the Senate and returned to his office in the Dirksen Building when news reached him of the shooting at the Capitol. Moments later, he was sprinting across the street to the scene of the carnage. Frist ran out of the office so quickly he left behind the medical bag he keeps there, according to spokesman Margaret Camp.

He performed CPR on one man "who had multiple gunshot wounds to the extremities" and the right side of the chest, and rode with him to D.C. General Hospital, the lawmaker told the Associated Press outside the hospital. Although Frist said he did not know the man's identity, he is believed to have been Russell E. Weston Jr., identified by police as the gunman.The senator also aided another man who had been shot in the face and helped load him into an ambulance. Again, Frist said he did not know the man's name. Two Capitol Hill police officers shot at the scene subsequently died of their wounds.

"I was really just focused on keeping their hearts and lungs moving," Frist said, calling the shooting "a very serious ca-tas-trophe."

It was not the first time that Frist, 46, offered medical treatment since he became a senator in 1995. That September, he administered CPR to a man from his home state of Tennessee who had gone into cardiac arrest outside the Dirksen building. When a rescue crew arrived, Frist inserted a tube into the man's lung to try to aid breathing and then used a defibrillator to jump-start his heart.

He has also come to the aid of Sen. Dianne Feinstein, D-Calif., when she grew short of breath from a drug allergy during a Senate hearing. Also, while on vacation in California in August 1996, he tended to a woman who had choked on her food.

Before entering politics, Frist taught at Vanderbilt University Medical Center and was the founding director of the Vanderbilt Transplant Center. He has written a book and was the editor of another on organ tranplantation.