The bullet was up there, somewhere in the darkened sky above downtown St. Louis, plummeting down, its path aimless, without intent.

No one below the bullet's silent trajectory had a clue. And maybe no one ever would have known had the bullet fallen a few inches to one side or a few minutes later.

But about 9 p.m. on a recent Sunday, in a parking lot outside Busch Stadium, as the crowd fanned out from a ball game, the bullet struck. It hit a 19-year-old Army soldier waiting for a bus back to Fort Leonard Wood. He was lucky. The bullet landed like a bird on his shoulder. It failed to penetrate his shirt. The bullet bounced to the ground.

Police called it "errant gunfire." No one heard a gunshot. No one saw a gun. There was no foreshadowing of fear. It must have seemed like the sky was raining bullets, like when you feel a single raindrop and wonder if it was a fluke or a storm's first sign. That's what made it so alarming. The usual precautions taken to ward off danger - the decisions on where to go, what to watch out for - were of no use.

It was a stray bullet.

A stray bullet travels for city blocks and country miles. It flies through downtowns, suburbs and farm fields. It is fired by thugs, hunters, police, revelers and target shooters.

Last summer in O'Fallon, Mo., a bullet grazed the leg of a lifeguard at a subdivision swimming pool. Police blamed people target shooting a mile away. That same week in St. Peters, a gun fell from a man's pocket at a gas station, hit the ground and sent a bullet into another man's wrist. A couple of months before that, stray bullets flew into occupied homes at a St. Charles County subdivision. And in the Metro East, a stray bullet last year flew three blocks before piercing a window and then the eye of a 21-month-old boy as he rocked in his great-grandfather's arms. Police in Madison blamed a gunfight.

In March, a stray bullet fatally struck a woman driving down a St. Louis street. Two months later, a stray bullet claimed a 7-year-old girl on a playground near downtown.

The stray bullet flies here and there.

In just the past month across the nation, stray bullets have hit people sitting on front stoops in Philadelphia and Brooklyn, a student in Tuscaloosa, Ala., a nurse in Palmetto, Fla., a man in San Francisco, a teenage girl in Springfield, Mass., toddlers on Staten Island and in the Washington suburbs, a child in Oakland, Calif., and a 10-year-old boy playing outside in Durham, N.C.

Despite such carnage from "errant gunfire," public health officials know little about it. The U.S. Centers for Disease Control and Prevention tracks accidental shootings. But they do not count stray bullets.

Dr. Garen Wintemute wanted to know more. He is a professor of emergency medicine at the University of California-Davis. Wintemute and his colleagues first had to decide what made a bullet a stray one. They came up with a bullet that "escaped the sociogeographic space or perimeter customarily set by the circumstances surrounding the firing of the gun ..."

Basically, Wintemute said in an interview, you know it when you see it. A bullet fired at five men on a corner but that hit the wrong person was not a stray. But it was stray if the unintended victim stood a block away.

Wintemute and researchers, using a single year of media reports of shootings from 2008 and 2009, found stray bullets injured or killed 317 people. More than 80 percent of the victims had no idea they were in danger until they were shot. About 40 percent were at home. And 20 percent died, making stray-bullet incidents just as lethal as those when bullets strike their intended targets.

The research, the first national study of stray-bullet shootings, was published last month in the Journal of the American Medical Association.

Wintemute said he was stunned by how little can be done to avoid a stray bullet.

"One of the things that we found so compelling is how unintended the person is," he said, "how random it seems."

Like a bullet falling from the sky outside Busch Stadium.

The bullet came down in the 800 block of Cerre Street, a dead-end road lined by parking lots crammed between the elevated roadway of Highway 40 and busy railroad tracks. There is the deserted husk of a sports bar, and next to it, the bustling horse stable for St. Louis Carriage Co., which provides carriage rides downtown. Horses are perhaps the only animal more skittish about gunfire than humans. It is quiet around here, said manager Jenny Holzum, who lives with two protective dogs in an apartment above the stable.

City police said they were working to determine if a bullet found at the scene was the bullet that struck the soldier, leaving the impression the street was littered with hot lead.

"I've never come across a bullet," Holzum said. "The thought has never crossed my mind until now."

The debris along Cerre Street one recent day was mostly a catalog of ordinary St. Louis diversions - Bud Ice bottles, strands of Mardi Gras beads, discarded Energizer AA batteries, St. Louis Bread Co. napkins, cigarette boxes, a Westwood Country Club cup, a tag for a "$30 XXL Pujols T-shirt."

A stiff wind fluttered a piece of yellow police tape tied to a chain-link fence. And just a few feet away, almost hidden in weeds poking through the asphalt, sat the empty packaging for an HKS Speedloader, model 36-A, promising to "reload revolvers instantly," perhaps perfect for helping speed a stray bullet on its way, into the sky, about to make its uncertain way down.