MENLO PARK, CALIF., DEC. 28 -- Cheryl Grass was watching fireworks last summer outside her workplace when an inch-long bullet fell from the sky, penetrated her thigh and lodged in her calf muscle.

Moments before, in a residential neighborhood on Henderson Avenue more than a mile away, a man had just fired the .30-caliber hunting round. Police arrested the 24-year-old gunman, but it was not until five days later that analysts at the county crime lab determined the bullet came from the man's gun.

The bullet was removed surgically, and Grass survived the Fourth of July incident.

But the only documented, injury-producing "celebration shot" in the United States proves what ballistics experts have known for years: Such celebrations can be dangerous, if not fatal, when negligent gunfire is involved.

Menlo Park police, determined to prevent similar injuries, have prepared a campaign against gunfire celebrations for New Year's Eve.

Called "Operation: Safe Skies," the program requires all officers to work the holiday, including the chief of police. Each will be assigned to tactical teams that will patrol city streets, especially the Belle Haven area, where most of the gunfire occurs.

In what may seem a militaristic approach, police have borrowed two night scopes, an armored car and two submachine guns and will don U.S. Army-issued combat helmets for protection. Officers even spent a day this week training in tactical maneuvers at Fort Ord.

Police Chief Bruce Cumming said the aggressive campaign is necessary at a time when citizens increasingly are arming themselves and becoming more blase about the dangers of gunfire.

As on past holidays, the department has posted flyers in Spanish and English warning that shooting guns in public places is dangerous and illegal.

"This is a serious matter. Some people fire guns celebrating and think it's no big deal. It is a big deal," Cumming said. "I'm really trying to approach it with education and enforcement. I'm hoping people will read the flyer and think twice about firing guns."

A 7-year-old girl was the victim of a falling bullet in July 1989. The bullet, believed to be a .38-caliber pistol round, went through her skull and lodged in the base of her brain, where it remains. The girl is recovering, police said, although she suffered some loss of memory and motor skills. Doctors told the family removing the bullet would damage the child's brain further and could kill her, police said.

Investigators followed up on every lead they had, but never found the gunman.

Ballistics specialists said handgun and rifle bullets fired at an angle of 30 degrees to 50 degrees can reach distances of 1 1/2 to 3 miles.

Each bullet hits the earth at a different velocity depending on size and shape but, in general, bullets come down much slower than they ascend because of air resistance.

Police said gunfire in eastern Menlo Park has increased noticeably over the years. Menlo Park's neighbor, East Palo Alto, is particularly notorious for the rat-a-tat of guns that typically begins around 7 p.m. and reaches a peak at midnight New Year's Eve. Firefighters at the East Palo Alto station said in the past they have put pots and pans over their heads to protect themselves when they stepped outside to listen to the gunfire.

Residents who stay indoors should be relatively safe, barring bullets flying through skylights or windows, but police out on the street will have to contend with the possibility of being struck by flying bullets.

Cumming said "Operation: Safe Skies" is not a disguise for SWAT maneuvering.

"Our officers are not going to do anything they aren't normally trained for. They're going to respond as they normally would respond to a report of a shooting or any incident. We want to put out the correct message: We're concerned for everyone's safety."