Adam Mosseri, the CEO of Instagram and a longtime Facebook employee, became a target of an anonymous online attacker who called in a fake hostage situation at his San Francisco home last November. The phone calls eventually led a SWAT team to Mosseri’s door, according to a new report in The New York Times that was published on Thursday.

The practice, known as swatting, has long been a particularly extreme form of online attack, and in some situations, it has even led to violence. After a Kansas swatting attack over an online match of Call of Duty led to the accidental police shooting of a 28-year-old Wichita man in 2017, the perpetrator — a serial swatter who had also called in numerous bomb threats in years prior — was sentenced to 20 years in prison. Two other men were charged with crimes related to the incident.

According to the NYT, which cites conversations and records with local police departments, swatting and similarly extreme online harassment has become more common in the San Francisco Bay Area and Seattle where many wealthy tech executives reside. The report says people have been using swatting, in particular, to target Facebook employees.

The NYT says dedicated swatting forums, many hidden from public view on the dark web, contain sensitive information about Facebook employees. Conversations on those forums seem to indicate that Facebook and Instagram employees are prime targets due to both companies’ policies on cracking down on fake accounts and certain types of speech.