In 2017, more officers were shot responding to domestic violence than any other type of firearm-related fatality, according to the National Law Enforcement Officers Memorial Fund. From 1988 to 2016, 136 officers were killed while responding to domestic disturbances such as family arguments, FBI data show. By comparison, 80 were killed during a drug-related arrest in the same period.

And in just the first few months of this year, six officers have died in domestic violence-related shootings, reports USA Today .

The pattern of repeated abuse makes domestic violence calls particularly dangerous for officers. A 2008 study by the National Institute of Justice determined that victims of domestic violence are more likely to call the police after repeated assaults have already taken place — which puts police officers in an even more volatile situation when they do respond.

“If someone breaks into your home, you’re going to immediately call police. You’re not going to let someone break in 10 times. But with domestic violence, it’s unique in that way, that the call could represent something that’s been percolating over time,” says David Chipman, senior policy adviser at the Giffords Law Center to Prevent Gun Violence and a former agent at the Bureau of Alcohol, Tobacco, Firearms and Explosives for 25 years.