The number of police officers slain in the line of duty nearly doubled to 51 in 2014 over the previous year, the FBI said in a report released Monday. But the sudden spike was largely due to a relatively low number in 2013, and the overall figure still appeared in line with a general downward trend.

The FBI report comes amid heightened debate about overall policing practices and police treatment of people of color, with officers who used deadly force often citing fear for their lives as the reason for pulling the trigger, as was the case when white police officer Darren Wilson killed unarmed black teenager Michael Brown in Ferguson, Missouri, after a scuffle on Aug. 9. The incident — and a grand jury decision not to indict Wilson — prompted protests across the country and has focused increasing attention on the issue.

Despite the sudden spike in the killing of officers last year, the level was still lower than in 1964 when 150 police died, according to the National Law Enforcement Officers’ Memorial Fund. The data correspond with a steep nationwide drop in violent crime, which has fallen by half since 1991.

In 46 of the 51 cases in the FBI report, the killer or killers used a firearm. In all of the killings, the alleged perpetrators were arrested or dispatched by “exceptional means” — an FBI term that the bureau says often means “the death of the offender (e.g., suicide or justifiably killed by police or citizen)” or “the victim’s refusal to cooperate with the prosecution after the offender has been identified.”

The 51 deaths represent an 89 percent increase over 2013, a particularly quiet year for law enforcement deaths, with just 27 reported. That was the lowest in the last 35 years, with an average of 61 officers losing their lives in the line of duty each year.

Accidents, often traffic-related, were the second-highest cause of officer deaths behind intentional killings, according to the FBI report.

“An additional 44 officers were accidentally killed in the line of duty in 2014,” the report said. “This total represents five officers fewer than the 49 officers who were accidentally killed in 2013. By region, 19 officers died due to accidents in the South, 13 in the West, seven in the Northeast, four in the Midwest, and one in Puerto Rico.”

In Hattiesburg, Mississippi, police officers Benjamin Deen and Liquori Tate suffered fatal gunshot wounds during a traffic stop Saturday night. Authorities arrested four people, charging two of them with capital murder, the Associated Press reported. It was the first time in 30 years that a police officer died while on duty in the rural town.