The family of Parkland, Florida, activist David Hogg was swatted, the Broward County sheriff’s office confirmed on Tuesday.

According to law enforcement, someone called the sheriff’s office claiming there was a hostage situation at the Hogg family home. Authorities went to the home and no sign of a hostage situation. It was a prank.

Hogg was not home at the time, the ABC affiliate Local 10 reported. He’s in Washington, DC, with his mom accepting an award.

It’s not clear who swatted Hogg’s family or why. But Hogg has been the target of vitriolic comments and attacks following the Marjory Stoneman Douglas High School shooting in February, as he became a vocal advocate for gun control. Right-wing pundits in particular have taken personal jabs at Hogg, with a conservative commentator from the Sinclair Broadcasting Group resigning after he threatened “to ram a hot poker up David Hogg’s ass.”

The swatting prank, though, takes things to a whole new level — potentially putting Hogg and his family in danger.

What is swatting?

Swatting is the act of calling 911 and lying about someone doing something really bad, like holding a hostage, to get dispatchers to send police officers — and particularly a militarized SWAT team — to a victim’s location.

Hogg is not the first high-profile victim of swatting. By the Associated Press’s count, other well-known victims include Tom Cruise, Justin Bieber, and Chris Brown.

It’s extremely dangerous. Police respond to the calls expecting a tense, violent situation, potentially making them more prone to shooting and killing someone. Last year, Wichita, Kansas, police killed 28-year-old Andrew Finch after a California man called the police to Finch’s home due to an argument in an online multiplayer session in the game Call of Duty: WWII. Finch was not involved in the argument, but his address was posted during the spat.

Swatting has become a part of broader internet trolling culture, particularly against high-profile figures and gamers who live-stream their play sessions, sometimes as their full-time jobs.

Here’s one example from 2014, in which someone playing Counter-Strike: Global Offensive got swatted:

The victim in this video, Jordan Mathewson, was in his office, streaming himself playing Counter-Strike, when he began hearing noises in the background. “Uh-oh, this isn’t good,” he said. “They’re clearing rooms. What in the world? I think we’re getting swatted.”

He was right. Pretty soon, a police team came through the door, telling Mathewson, “Don’t you fucking move.”

The Littleton, Colorado, police department later said in a statement that a caller “claimed to have shot two co-workers, held others hostage, and threatened to shoot them. He stated that if the officers entered he would shoot them as well.” So police responded with force.

As the local police chief later said, “This is not a game. This is not an online game. We have real guns with real bullets, and there’s a potential there for some tragedy.”

On top of endangering everyone involved, swatting is a total waste of law enforcement resources. As the FBI explained in 2008, “[T]hese calls are dangerous to first responders and to the victims. The callers often tell tales of hostages about to be executed or bombs about to go off. The community is placed in danger as responders rush to the scene, taking them away from real emergencies. And the officers are placed in danger as unsuspecting residents may try to defend themselves.”

Who would do this?

It depends.

Some swatters are trolls who do this for laughs and personal entertainment. Research shows that internet trolls tend to display personality traits like sadism, psychopathy, and Machiavellianism. So in some cases swatting is just manifestations of someone’s sadism.

Some people have also used swatting to blackmail others. Jason Fagone reported in New York Times Magazine in 2015 on a serial swatter who used the threat of swatting — and other intrusions into people’s lives — to coerce girls to be his friend and, among other things, force them to send nude images to him:

Online abuse began to cross over into the physical world. He sent pizzas to their homes. A string of deliverymen climbed the stairs to K.’s apartment in Florida, carrying unappetizing pies: deep-dish pizza with no cheese, pizza with anchovies and jalapeños, double bacon and double pepperoni. He called their cellphones repeatedly and sent “text bombs” of hundreds of messages at a time. If all else failed and Obnoxious couldn’t get a hold of a woman, he would start threatening to dispatch a SWAT team to her house, or her parents’ house, or her college — a kind of intrusion that couldn’t be ignored.

Other groups of people use swatting for political and social causes.

As Brian Resnick explained for Vox, many people will show their outrage for someone’s actions or beliefs — both for their personal entertainment and to demonstrate their moral character to others — by joining in social media mobs to punish someone for perceived wrongdoing.

This has certainly happened to Hogg, with people personally attacking and harassing him as a result of his advocacy for gun control. Swatting may be an outgrowth of this kind of behavior: If thousands or millions of people dislike Hogg because of his political beliefs, it only takes one of those people to go way too far and call the cops on Hogg’s house.

How do we stop swatting?

Like typical crimes, it’s impossible to stop all swatting. But there are some precautions that different levels of government, along with internet services, can and do take to help prevent it.

The law already punishes swatting, with some swatters sent to prison in recent years. In 2015, a Connecticut man got a year in prison for swatting. In another case, a Nebraska man who was part of a swatting ring was sentenced to five years in prison. And this past year, the man who swatted Andrew Finch in Wichita was charged with involuntary manslaughter, giving false alarm, and interfering with law enforcement.

Some law enforcement agencies have also taken on the issue by themselves. After an increase in swatting cases, several California police agencies told the AP they’re taking more steps to gauge which 911 calls are real and holding back a bit before deploying their full resources, like a SWAT team.

If any good comes out of swatting, it could be these types of changes. There’s a lot of evidence that police are way too quick to deploy their militarized units. A Washington Post investigation found, for example, that police in Washington, DC, frequently raid the wrong homes on bad, little, or no evidence, terrorizing innocent people.

Radley Balko, the author of Rise of the Warrior Cop, has documented many situations in which police use SWAT teams on completely nonviolent offenders, from marijuana growers to poker players. And a report from the American Civil Liberties Union found that 62 percent of analyzed SWAT deployments in 2011 and 2012 were for mere drug searches.

In fact, some have argued that swatters merely take advantage of a system that’s way too quick to use force. Fagone explained for the New York Times Magazine:

The Georgia tactical commander, a veteran of the Marines, says that for planned raids, when he and his team are considering whether to deploy, they use a “matrix” of risk factors to decide if a SWAT response is justified: Does the suspect have a history of violence? Does the suspect have weapons? Has the suspect made threats to law enforcement? For a situation in progress, though — an emergency call — there is no time to go through all of that, and from a police point of view, it’s better to “respond high and then downgrade” than it is to show up unprepared. So when a situation arises with a possible active shooter, especially one who says he is heavily armed and will kill officers, dispatch sends a text to team members’ cellphones to respond to a certain address, and the police are ready for confrontation. And when the police “respond high,” residents can become disoriented. Maybe they assume they are being robbed. Maybe they pick up a gun. In 2011, a former Marine and Iraq war veteran named Jose Guerena was awakened by his wife, who thought she saw intruders outside their home in Arizona. Guerena picked up his AR-15 rifle, with the safety on, to protect his wife and family. SWAT officers entered the house, saw the gun and shot Guerena dozens of times, killing him. They were conducting a drug investigation. In 2010, during a military-­style raid on a home in east Detroit, a police officer looking for a murder suspect accidentally shot and killed a 7-year-old girl while she slept.

Given these stories, it’s a fair question: Should one phone call really cause the police to deploy a militarized unit into someone’s home?

Part of the problem may be that society just doesn’t take swatting seriously enough. Police agencies may see swatting as a one-off prank, not as part of a pattern of harassment and abuse that can happen on the internet. Internet services may not stop harassment until it spirals out of control — something companies like Twitter have been heavily criticized for. And friends and family may blame the swatting victim by questioning how he or she got into so much trouble that someone called a SWAT team on them.

But even if all of this changed, stopping swatting is really hard. Sometimes police just can’t tell if a call is real, and law enforcement need to respond to emergency calls in some fashion. And trying to deter swatters with tough criminal sanctions won’t do much if people think they can get away with the crime — and they often can by, for example, using hard-to-trace internet phone services or prepaid phones.

The ultimate solution, then, may be for people to stop being jerks on the internet. But since that’s not likely to happen anytime soon, swatting will continue — putting people’s lives at risk, sometimes for no reason other than some laughs.