WASHINGTON (AP) — The number of law enforcement officers killed as a result of criminal acts decreased in 2015 from the year before, dropping from 51 to 41, the FBI said Tuesday.

The report covers officers who were killed during ambushes, traffic pursuits, tactical situations, domestic disturbance calls and while handling prisoners and individuals with mental illness, among other situations.

More than half of the officers killed were on vehicle patrol when they died. Most who died — 38 — were killed with firearms.

In addition, more than 50,000 officers were assaulted last year while performing their duties, the FBI said. And the report says 45 law enforcement officers died accidentally in the line of duty, many during automobile and motorcycle accidents.

The report includes the cases of a Philadelphia police officer who was killed during a robbery attempt; a New York City police officer fatally shot while investigating a suspicious person; and an Omaha, Nebraska, officer who was slain while pursuing a fugitive just as she was about to go on maternity leave.

It's too early to know what the 2016 tally will be, but there have already been a series of high-profile police deaths this year, including the five officers in Dallas who were slain by a sniper over the summer and three law enforcement officers who were killed in Baton Rouge, Louisiana.