"There was, I think , a very quiet arrival," Jerry Parr related in a deep, calm voice as he began his narrative. "And basically a quiet departure, until the gunfire."

Before a spellbound Senate subcommittee yesterday, Secret Service agent Jerry Parr, the man who grabbed President Reagan and threw him into the limousine at the Washington Hilton Hotel Monday, spun out a second-by-second account of the wounded president's escape after six shots were fired by an assailant a few feet away.

It was a blood-and-guts tale of good luck and bad, of fantastic bravery and fouled-up communications. Parr told of a jovial, kidding president who suddenly turned ashen and started coughing up bright red blood -- and then had to walk into the hospital emergency room because no one thought to bring out a stretcher.

Parr, a tall, gray-haired, 50-year-old Secret Service veteran who began his career as an agent guarding the late Hubert H. Humphrey in 1964, made; what was essentially a command appearance before a subcommittee that was hearing testimony from his superiors.

When the senators learned that Parr was in the audience, they gave him an ovation. "You made a great impression on the Gipper," said Sen. Paul Laxalt (R-Nev.), one of Reagan's closest personal friends. Then the senators asked Parr to step forward and narrate the events of Monday afternoon.

Like all the other Secret Service officials who discussed the attack, Parr began by noting that he knows of no striking security failures, or anything his agency could have done differently to prevent the incident. "I felt very comfortable . . . until the gunfire," he said.

Parr said he never saw the gunman, because "the gentleman was shielded . . . . I heard the gunfire and immediately moved the president left, down, and forward into the car. Basically, it was an instinctive reaction. . . . I reacted to the sound. Basically, we seek the most safest place. For me, it was behind the door and into the car."

At this point, Parr was asked how a fellow agent, Timothy J. McCarthy, found the courage to turn toward the gunman and apparently take a bullet in the stomach deliberately. "That's a hard question to answer," Parr said. "We are all trained to put ourselves between an assailant and the president.

"[But] I think what agent McCarthy did was most heroic. It seems like to me that he . . . made himself bigger than life and interposed himself between the assailant and the president, and probably saved the president's life or my life.

"McCarthy, I think he responded to that first shot . . . and took it. At the same time as the other shots were going down, we were behind that door and into the car . It was just one piece, one flow, one action by a lot of people, Parr said."

Returning to his narrative, Parr next related what happened after he pushed Reagan into the limousine.

"When I went in on top of the president," Parr said, "he and I landed on top of the transmission riser that's in between the two seats."

After the hearing, Parr told reporters that, as they sped down Connecticut Avenue seconds after the shooting, he and Reagan joked about their flying entrance into the car. "He said, 'Hey, c'mon, you really came in hard on me.' We were kidding about it," Parr said.

As soon as he and the president leaped into the car, Parr recalled, "I told the driver, Drew Unrue, to leave rapidly, and he did.

"I pushed [Reagan] up to the right rear . . . his normal position for riding in that car is the right rear. I ran my hands over his body . . . looking for some kind of a wound.

"He claimed that I had hurt his ribs in landing on top of him. So at that time, I told the driver to head to the White House, the safest place.

"Shortly after that, I would say in a space of 10 or 15 seconds, he complained of a problem in breathing, he was getting a bit ashen in color, and then he started coughing up a little blood. It was bright red, and I knew from my training that this was oxygenated blood, this blood coming out of the lung."

This occurred, Parr said, just as the limousine was in the tunnel beneath Dupont Circle. As soon as he saw the blood, indicating a wound in the lung, Parr went on, "I told the driver to head for on, "I told the driver to head for George Washington [Hospital]."

Laxalt asked Parr why Reagan walked into the hospital. "This is a very fuzzy area," the agent replied. "It seemed like the most natural thing to do. There was not a stretcher there, although they did know we were coming.

"So we got up, and [we] took him by the arm, two or three of us, and walked him in . . . I asked for assistance of two or three agents in the followup car behind us.

"He got up, walked in, approximately 45 or 50 feet. I felt he was perhaps going into shock, he started to buckle a little bit, and we carried him the rest of the way into the trauma unit. The trauma unit started to work on him immediately. I asked [agent] Ray Shaddick to secure a [security] perimeter, which was done."

After Parr had finished his quiet, almost monotonous presentation of this graphic tale, the members of the Senate Subcommittee on Treasury Appropriations crowded around to congratulate him. "I've got to have a picture with him," said chairman James Abdnor (R-S.D.).

Laxalt came over and gave the agent, who is chief of the presidential protective details, a long handshake. "If it weren't for you," Laxalt said, "I think our guy might not have been around."

"Well," Parr replied calmly, "God was on our side."