Secret Service officials said yesterday that agents guarding President Reagan followed prescribed procedures to the letter at the Washington Hilton Hotel Monday, but the agency is looking into whether the president's waiting limousine may have been parked too far from the door.

When Reagan came out of the Hilton Monday, the bullet-proof presidential limousine was not waiting directly in front of the hotel exit, as Secret Service practice usually requires.

If it had been, Reagan would have had a straight-line walk of about eight feet from door to car. Instead, he had to walk diagonally down the sidewalk about 25 feet, bringing him around a curve and into the line of fire of accused assailant John W. Hinckley Jr.

There was no clear answer yesterday why the car was not immediately outside the door or whether events would have happened differently if it had been.

As the FBI, D.C. Police and Secret Service began investigations of the assassinations attempt, those questions seemed likely focal points, as were two other queries:

Why didn't the Secret Service have any warning about Hinckley and his previous firearms record? The agency's initial answer was that Hinckley's arrest for carrying three concealed handguns last October was not the kind of charge that triggers Secret Service attention.

How did Hinckley manage to get into the press area outside the Hilton about 10 feet from the president? A Secret Service official said the advance agent on the scene concluded that it would be counterproductive to set up an area restricted only to the press on the narrow, curving walk outside the hotel.

The basic dilemma posed by the shooting, security officials said, is the impossibility of providing total protection for anyone in a public place in a free country.

One Secret Service agent recalled a comment attributed by author Jim Bishop to the late President John F. Kennedy: "No amount of protection is enough. All a man needs is a willingness to trade his life for mine."

And, although the Secret Service keeps computerized records on about 20,000 people who have come to its attention as potential threats to a president, the list cannot be complete. None of the six people involved in prominent assassination attempts since 1963 was ever on the list.

If a president can be protected anywhere, security officers said, it would be at a major hotel in Washington where Secret Service and police officers are on familiar turf.

That is particularly true at the Washington Hilton, the hotel probably visited most by presidents for speeches and dinners. Reagan was shot as he came out of an unmarked security exit the hotel had installed, with Secret Service guidance, to provide safe passage for presidents and other VIPs.

Given the dimensions of the problem, Secret Service officials said yesterday that the agents with Reagan had done everything possible. "After viewing the video Tapes," agency spokesman Jack Warner said, "we believe the presidential protection was as effective as it could possibly be. These guys were competing with a bullet."

Secret Service agents not on the Reagan detail pointed out that those at the Hilton did exactly what training manuals prescribe.

One agent, Timothy J. McCarthy, turned in the direction of the shots and took a bullet aimed toward the president in his chest. The chief of the Reagan detail, Jerry Parr, Grabbed the president and threw him into the limousine.

"This is rule No. 1 when something happens," an agent explained."Find an escape route. Get the man out of there."

Generally, agents want the armored limousine waiting in a direct line with the president's exit door as he moves from building to car.

Such positioning shortens the period of vulnerability and makes it easier for agents to form a human shield as the public figure moves. In some cases, agents have had the car moved one foot or less to have it perfectly aligned with the exit.

On Monday, though, Reagan's limousine was waiting about 20 to 25 feet down the driveway from the door. To reach the car, Reagan had to walk down the curving sidewalk. Around the curve, flush against the hotel wall, the assailant waited with his pistol.

Asked about this yesterday, Secret Service spokesman Richard Hartwig noted that if the limousine had been waiting in the narrow driveway directly outside the security exit, it would necessarily have been heading downhill, or east, to drive out of the hotel complex to T Street.

Instead, the car was facing west, uphill toward Connecticut Avenue. Because of a traffic island that blocks access to T Street just in front of the security door, a westbound car would have to wait two car lengths below the door to pull directly onto T street. Otherwise, the car would have to circle through the hotel's front driveway before reaching the street.

Hartwig speculated that the car was facing west below the security door so Reagan could enter by the right rear door, which the service considers the the safest "VIP position" because it provides a direct sight line for agents riding immediately behind in a motorcade.

But Hartwig said the question must be considered more fully.

The Secret Service's ignorance about Hinckley and his firearms record resulted from what Hartwig called "a judgement call, not clear one way or the other."

"We understand that he was arrested at an airport [in Nashville] with concealed handguns," Hartwig said. "That in itself was not enough to notify the Secret Service. Now, the fact that the president [Jimmy Carter] was in that city on the same day, apparently nobody made the connection."

Hartwig said it is not clear whether Carter's presence would have made the incident something the Secret Service should have been told about.

Television crew members at the Hilton said they had complained to the Secret Service about bystanders pushing into the area reserved for the press. One bystander, as it turned out, was the accused gunman.

A Secret Service official said the press area outside the hotel was not a "dedicated press area" -- that is, not an area with access restricted to those with press credentials.

The official said the agent who set up the area before Reagan's arrival decided that a restricted press area would compound security problems. It would force onlookers, he said, to spread out along the curving walk, perhaps to the other side of the driveway, making protection more difficult.

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