Police officers across the country handle some of the most dangerous situations in our society on a daily basis. A Statistics Canada study released in 2010 found that with the exception of taxi drivers, police are the most likely Canadians to be slain on the job.

The latest reminder of just how dangerous policing can be came Friday in Fredericton, N.B., where officers Lawrence Robert Costello, 45, and Sara Mae Helen Burns, 43, were among four people killed in an early-morning shooting.

The Canadian Police And Peace Officers Memorial database contains a near complete accounting of all law enforcement personnel who died while on duty. CBC News analyzed these records to uncover the key trends on police fatalities since 1975.

Homicide most common cause of on-the-job deaths

Since 1975, a total of 284 police officers have died on the job. Of these, 101 were homicide victims, while 88 were killed in vehicle accidents — often while rushing to respond to a call in poor road conditions.

Aircraft crashes during transportation or surveillance operations in more remote regions account for 29 deaths, and often claimed many lives in a single crash. On three occasions, officers were killed during training exercises.

Firearms often used to kill police

More than 83 per cent of slain police officers were killed with a firearm. In 11 cases, the assailant used a vehicle or a knife as the weapon. Overall, the number of police homicides is in decline since the 1970s.

The Statistics Canada study from 2010 found that about 80 per cent of officers killed with a firearm were not wearing bulletproof vests. However, this trend has decreased significantly since the mid-1980s.

The same study found most officers were attacked by surprise — only a third had the chance to draw their gun or fire a shot before their death.

Robbery calls led to most police deaths

Using cases up to 2009, Statistics Canada found robbery investigations have led to the most police deaths, accounting for a quarter of cases. Overall, domestic calls are the second-most likely scenario in which police are murdered, but in recent years, roadside stops and suspicious people calls have increasingly lead to more fatalities.

RCMP has suffered the most losses

Nearly 30 per cent of police homicide victims were members of the RCMP. In many cases, more than one officer was killed during the same event, such as in the 2014 shooting in Moncton, N.B., where three officers were murdered, and in Mayerthorpe, Alta., in 2005, where four officers were shot and killed.

A total of 28 Mounties have been killed in homicides on duty since 1975. The Montreal police service is next with 11 officer homicides, followed by the Ontario Provincial Police with 10.

In 40 per cent of homicide cases, the officer was responding to a call alone.

Homicide victims are mostly young, less-experienced men

Sara Mae Helen Burns, who was killed Friday in Fredericton, is only the fourth female police homicide victim since 1975.

Historically, the average age of officers killed on duty is 34 years, with about eight years of service.

U.S police more likely to die by homicide

Over the past decade in Canada, there has been an average of 1.8 police killed by homicide per year. Statistics Canada estimates there are about 70,000 sworn officers in the country.

In contrast, figures from the U.S. National Law Enforcement Officers Memorial Fund show there is close to one police officer killed on the job per week. The Bureau of Justice Statistics pegs the total number of sworn officers in the U.S. at more than 750,000.

Police homicides occur most often on Fridays

Of the 101 police homicides since 1975, a quarter of them have occurred on a Friday.

Notes on methodology: