By CLIFFORD KRAUSS

All but one of the eight gunshots that turned a crowded East Side subway station into a battlefield Monday night were fired by police officers mistakenly aiming at each other, police officials said yesterday. The remaining shot, they said, occurred when a suspect dropped his shotgun and it went off.

In the tumult, an off-duty New York City police officer opened fire on a black undercover transit officer, hitting him four times, at least twice in the back, the officials said.

The incident, which began when passengers reported seeing two teen-agers with guns in the 53d Street subway station, ended with the transit officer, Desmond Robinson, critically wounded; the city police officer, Peter Del Debbio, was shot in the arm, and a civilian, Patricia Coples, was struck in the legs by shotgun pellets.

The shootings raised questions once again about police safeguards intended to protect undercover officers from so-called friendly fire. The shooting of Officer Robinson also focused attention on whether black undercover officers are more at risk in such confusing situations.

Police Commissioner William J. Bratton said he would consider instituting in his own department the training that transit officers already receive to teach them to recognize that a person who appears to be a suspect may actually be an undercover officer.

But he defended the actions of his department and those of Officer Del Debbio, who opened fire on Officer Robinson. Although the investigation is not complete, Mr. Bratton said, police officials have so far concluded that Officer Del Debbio made a snap judgment that was tragic but understandable.

"This was 15 seconds of sheer terror for these two men who did what they were supposed to do," Mr. Bratton said. "We're not going to second-guess them."

But the Guardians, a black officers' association with chapters in both the city and transit police forces, saw the incident differently, saying it could have been averted with better training. They called for the arrest and prosecution of Officer Del Debbio for shooting Officer Robinson.

"To shoot him three times in the back is out-and-out murder -- period," said Sgt. Kelvin Alexander, the president of the transit police unit of the Guardians. "And he should be prosecuted to the full extent of the law. I don't think he knew it was a cop. He was just killing another black man, and that is indicative of a sickness right there."

Several crucial questions remain unanswered, including why neither Officer Del Debbio nor Officer Robinson apparently identified himself as a police officer, and why Officer Robinson was not displaying his badge or wearing the colored bands that undercover officers often use to identify themselves to other officers.

Mayor Rudolph W. Giuliani held a news conference at City Hall yesterday in an attempt to play down the racial issue, and police officials repeatedly said Officer Del Debbio is Hispanic. The officer's mother is Puerto Rican, and his father is Italian-American.

Officials also noted that Officer Robinson was in civilian clothes as a member of an undercover squad seeking pickpockets.

"It would really be unfortunate for people to draw conclusions," Mayor Giuliani said. "We should try to suspend judgment." He added that the two wounded officers were "acting as they have to act to protect others."

The events which led to the shootings began about 7 P.M., when two people leaving the station at 53d Street and Lexington Avenue told a uniformed transit police sergeant and his driver that they saw two armed teen-agers on the E and F subway platform. The two officers ran down the up escalator and were joined by Officer Robinson and his pickpocket detail in pursuing the teen-agers.

The sergeant captured Damal Parham, 16, as the youth dropped a .22-caliber derringer on the platform. The second suspect, Shea Kisine Davis, 17, ran, drawing a sawed-off shotgun from a slit in the leg of his pants, said Joseph Borrelli, the Chief of Detectives.

While Mr. Davis was trying to drop the gun between the parked E train and the platform, it went off with a sharp explosion, Chief Borrelli said, and some of the pellets struck Ms. Coples, who was not seriously injured. Then Mr. Davis ran into the Queens-bound E train, in which Officer Del Debbio was sitting, though apparently in a different car.

The police said the accounts of more than 40 witnesses differ in several respects at this point. But at least one witness said Officer Del Debbio crouched down on the subway car floor in a military-style firing position, with one knee on the ground, as he trained his gun on Officer Robinson through a door that repeatedly opened and shut.

Point-Blank Firing?

A 47-year-old New Jersey commuter named Dennis Kearns said he saw a man, later identified as Officer Del Debbio. kneeling with his gun over another man, later identified as Officer Robinson, who lay face down, half in the train and half on the platform. He said the kneeling man fired his gun three times at point-blank range into the other man's back.

Senior police officials disputed parts of Mr. Kearns' account, noting that he said the revolver Officer Del Debbio fired was a black automatic pistol, when it was actually a silver revolver. But the officials confirmed that Officer Robinson was shot several times in the back at close range.

"He could have been shot in the front and spun around," Mr. Bratton said, adding that the shots in the back did not necessarily suggest wrongdoing.

Seeing that his colleague had been shot, Officer Joseph Fitzgerald of the transit police opened fire on Officer Del Debbio, unaware that he, too, was a police officer. One of the rounds he fired from his 9-millimeter handgun ricocheted off the stainless- steel side of the train and hit Officer Del Debbio in the arm.

Officer Robinson and Officer Del Debbio are being treated at Bellevue Hospital Center, where Officer Robinson remains in critical condition.

Police officers have wide latitude in when to fire their weapons, especially when they believe their lives are in danger. In ideal situations, they are to identify themselves as police officers before they shoot.

"Nobody, none of the witnesses, indicate that any words were exchanged between the two officers, " Mr. Bratton said, noting that more than 30 witnesses had been interviewed.

Ideally, undercover officers wear the "color of the day," -- normally a headband or wristband of a specific color -- to identify themselves to other officers, and when making arrests or using their weapons, they take out their badges, which most undercover officers wear under their clothes on chains around their necks.

Police officials said that no one in the pickpocket squad was wearing the color of the day -- orange -- on Monday, and that Officer Robinson's badge was in his pocket. Michael O'Connor, chief of the transit police, said that the officer might not have had time to pull out his badge.

Officials also indicated that undercover officers do not always wear their color-of-the-day bands, instead sometimes putting them on only when they plan to draw their weapons or make an arrest, but they did not know if this was a violation of departmental policy.

The color of the day is the same for the New York City police, the transit police and the housing police, and written notices advising officers of the color are distributed to all offices of all three departments, officials said.

Of the two Queens teen-agers, Mr. Parham was charged with criminal possession of a weapon. Mr. Davis, the suspected carrier of the shotgun, was charged with assault, criminal possession of a weapon and reckless endangerment.

At the time of his arrest, Mr. Davis was being sought for questioning about a shooting involving a bike he was alleged to have stolen. The police said that Mr. Davis robbed a 17-year-old girl of her bike on July 27 and that when her boyfriend confronted him and took the bike back, Mr. Davis pulled out a .380-caliber automatic pistol and fired nine shots. No one was hurt in that incident.

Sergeant Alexander said he and other members of the Guardians would come to police headquarters today to show a training film the group produced two years ago after Derwin Pannell, a black undercover transit police officer, was shot and seriously wounded while making an arrest by a white colleague who mistook him for a mugger.

Copyright 1994 The New York Times Company