Statistics show that since 2000, there have been about 9.5 ambush killings of law enforcement officers per year nationwide, and that the number has been declining in recent years, to about six per year. But this year is off to a horrible start. There have already been five ambush killings in 2016.

There are roughly 59,000 assaults on police officers each year, according to the National Law Enforcement Officers Memorial Fund, resulting in more than 15,000 injuries. Statistics show that about 50 officers a year are killed in criminal incidents, excluding car wrecks and other causes of line-of-duty deaths, the Washington Post reports.

The International Association of Chiefs of Police published  a study in 2013  specifically analyzing police ambushes, where an officer is suddenly attacked without apparent provocation, and found that the average ambushed officer is a 38-year-old male with 11 years on the job. Of those killed, 38% were patrol officers, 17% were deputy sheriffs and 15% sergeants, all the most likely to be first responders to any 911 call. Colson was an undercover detective who just happened to be in a district station when a gunman started firing Sunday afternoon and officers returned fire.

Also a bad portent for 2016: firearms-related fatalities for law enforcement are up 225% through today, from four at this point last year to 13 so far this year, according to the NLEOMF .