On July 4th, 2013, 7-year-old Brendon Mackey of Virginia was walking with his father to go watch Independence Day fireworks at a public park near Richmond when he was struck in the head by a bullet; he died within hours. Two years later, authorities still have no idea who fired the .40-caliber handgun round that killed Mackey, although they are confident that the gun was fired into the air somewhere within a 7,200-foot radius of the young boy.

On July 4th, 2011, 11-year-old Blair Shanahan-Lane was in the yard of her uncle’s house in Kansas City, Missouri, when she collapsed to the ground. At first, her parents believed she had been hit by a firework; it soon became clear that she had actually been struck in the neck by a bullet fired from blocks away. Exhaustive canvassing of the area by police eventually turned up a group of men who admitted to shooting a pistol into the air to celebrate the holiday; the owner of the gun was later sentenced to three years in prison for involuntary manslaughter.

This Fourth of July weekend, as they do every year, Americans will mark Independence Day with more than just bottle rockets and sparklers; some will also fire their guns into the air. While the U.S. Consumer Products Safety Commission tracks injuries and fatalities resulting from fireworks (eight deaths and 11,400 injuries in 2013, with 75 percent occurring within the one-month period around July 4), there is no national-level data collection by the CDC or other agencies on casualties from celebratory gunfire. Nonetheless, information drawn from private sector “gunfire location systems” such as ShotSpotter, which uses audio-visual sensors and other techniques to locate and record gunfire, paints a provocative picture.

In the 48 communities where ShotSpotter’s equipment is deployed, the company reports, “Statistics show that there are strong seasonal gunfire periods, where approximately 15 percent of all annual gunfire incidents take place on the holidays around New Year’s Eve, New Year’s Day, and the Fourth of July. About two-thirds of that total is around the 4th of July and about one third is around New Years.” The overwhelming majority of those rounds will land harmlessly or lodge in roofs or other property. But in areas with high population density, some will inevitably hit human beings. And so, each year before those holidays, police, city officials, and activists from California to Ohio to Texas to Florida are compelled to call on their communities to desist from spraying bullets skyward.

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The impoverishment of data notwithstanding, it’s safe to stipulate at this point that the odds of any single person’s being hit by a celebratory round are extremely low. Even contentious research on stray shootings in general acknowledges that celebratory gunfire (wounds from “falling bullets”) represents less than 5 percent of all firearm-related injuries.

The incidents that fall into that sliver are the product of some lethal science. While rounds fired at a perfect vertical (which is actually difficult to execute even under controlled conditions) will lose their spin and tumble down, the physics governing ballistic trajectories means that rounds fired at angles of 20 to 45 percent in particular can retain lethal force at considerable distance. This is borne out by hospital admissions data from studies in LA, San Juan, and Pakistan, all of which indicate that falling bullets, when they do connect with bodies, are most likely to hit heads, shoulders, and feet, and can easily do extensive damage. Data also suggests that falling bullets are several times more likely to be fatal than other gunshot wounds, and that women and children specifically are much more likely to be injured by celebratory gunfire than by other kinds.

As some of those same studies indicate, celebratory gunfire is by no means a uniquely American phenomenon. People fire guns into the air to celebrate holidays and other events from the Philippines to the Balkans to the Middle East; just last month, a 19-year-old woman was accidentally shot in the head and killed during wedding celebrations in France. U.S. forces have blamed celebratory gunfire for mistaken bombings of wedding parties in Afghanistan.

But if the odds of being hit by celebratory gunfire are indeed low, so too are the odds of ever being caught for engaging in it in the U.S. Cases like Shanahan-Lane’s, where authorities can precisely pinpoint the location of the gun — let alone identify the shooter — are incredibly rare. The legal consequences for those who do get caught are incredibly mixed, with charges ranging from the misdemeanor to felony level and fines ranging widely.

And why do people do this in the first place? On one level, the answer is the obvious one: It’s recklessness, frequently abetted by drunkenness.

People may actually not realize that the bullets they launch into the air will inevitably land somewhere, with potentially disastrous results. But on another level, there are basic economics at work.

Many municipalities ban the sale of fireworks outright, meaning that residents have to be able to afford to travel outside city limits or even cross state lines in order to buy them. Meanwhile, ammunition can be plentiful, already at hand, and, in many cases, simply cheaper.

In the first minutes of 2010, four-year-old Marquel Peters was sitting next to his mother in a church in Decatur, Georgia, playing on a portable Nintendo, when a bullet sliced through the building’s roof and struck him in the head. He died shortly afterwards. Ballistics experts speculate that the round — likely shot from an AK-47 — could have been fired anywhere from a half-mile to three miles away; the shooter remains unknown. At the time, a Decatur resident would have had to drive an hour and a half into neighboring Alabama in order to buy fireworks. As of this past Wednesday, however, new legislation means that fireworks can now legally be sold in the surrounding county.

There is a licensed fireworks merchant, a Kroger, 20 minutes away from the church where Peters was shot, and a store that sells ammunition 10 minutes from it. At the former, a “variety pack” box of fireworks will cost $40 to $50. At the latter, AK-47 ammunition will run $30 for a box of 20 rounds.

[Photo: Flickr user !Koss]