Terrorism.
Via Washington Times:
The number of ambush-style killings of police officers in the U.S. reached a two-decade high this year, pushing law enforcement fatalities to their highest rate in five years, with 135 officers killed in the line of duty, according to a year-end report by the National Law Enforcement Officers Memorial Fund.
Shootings were the number one cause of death for law enforcement in 2016, claiming the lives of 64 officers — including eight gunned down in two ambush attacks in Dallas and Baton Rouge, Louisiana, in July. The report notes 21 of the officers were shot and killed in ambush-style attacks.
Firearms-related deaths were up 56 percent over the 41 officers killed by gunfire in 2015, but are still far below the all-time high of 156 officers killed by gunfire in 1973.