NEW ORLEANS (AP) _ Nobody knows who killed Amy Silberman _ maybe not even the killer.

But there are plenty of suspects in the death of the Boston tourist killed by a bullet that dropped from the sky and pierced her skull on New Year's eve.

``Everyone that fired a weapon on New Year's Eve is a suspect _ everyone that fired a weapon,'' Superintendent of Police Richard Pennington said Monday.

Silberman, 31, was in the French Quarter's Jackson Square near the Mississippi River at about 11:40 p.m. Saturday, awaiting the New Year's fireworks display.

Suddenly she fell down. She was taken unconscious to a hospital, where an X-ray showed the bullet in her head. She died Sunday morning.

And police were left with the seemingly impossible task of finding somebody, somewhere who was taking potshots at the clouds.

Pennington appealed to the public for help in finding anyone who might have fired a gun around the time Silberman was shot.

Ballistics tests were conducted Monday in the hope of identifying the type of weapon fired and, maybe, how far the unwitting killer was from Silberman.

Police spokesman Lt. Sam Fradella wouldn't speculate Monday when asked whether it was a question of feet, yards or miles. ``We're not going to eliminate any possibilities,'' Fradella said.

But he said the investigation would be helped by authorities in Jefferson Parish, less than a mile from the Quarter across the Mississippi River, and St. Bernard Parish, less than two miles from where the victim fell.

Every year, there are scattered reports in New Orleans and other areas of gunshots fired into the air to celebrate New Year's Eve, Independence Day and other holidays. Five injuries last year were attributed to such gunfire and police said three were reported during the New Year's weekend, despite public warnings that a bullet fired at the clouds returns to Earth with lethal velocity.

``I equate shooting in the air on New Year's Eve the same as shooting a gun into a crowd or the same as a drive-by shooting,'' Pennington said.

He announced last week new efforts to combat the practice, including a strong police presence in areas of the city where reports of gunfire have been most common in past years.

Silberman's death brought another shock of bad publicity to a city with an economy heavily dependent on tourism. New Orleans is among the nation's leaders in murders per capita and the 419 killings in 1994 _ 420 if Silberman's death is included _ by far surpassed the one-year record of 389 set last year.

Tourists were rarely among the victims. A visitor from Baton Rouge was shot to death in the French Quarter during an argument last fall and a German soldier was killed May 2 in an apparent robbery attempt.

``I knew she was going to New Orleans, but I didn't think anything would happen,'' said Sam Silberman, Amy's father. ``This just comes as such a shock.''

Beverly Gianna, director of public relations for the New Orleans Metropolitan Convention and Visitors Bureau, said she is confident police are doing all they can. She added that such problems are widespread.

``The focus has been on New Orleans, but it's a problem that every city in this nation is facing no matter how small or how big,'' she said.