The number of law enforcement officers killed in the line of duty nearly doubled last year from the year before, according to statistics released Monday by the FBI. There were 51 law enforcement officers killed in 2014, a significant increase over the 27 officers who were killed in 2013, the FBI said.

While the number of officers killed significantly increased last year, that total is still lower than what the country has seen in recent decades. Between 1980 and 2014, there were an average of 64 law enforcement officers killed each year.

In addition, the 27 officers killed in 2013 represented the fewest officers killed in any single year since 1980, so the uptick in 2014 came after a year with the fewest such deaths in a generation. (A different tally released by the National Law Enforcement Officers Memorial Fund last year found that the number of officers shot and killed has fallen each decade since the 1970s.)

These statistics are preliminary and more data is expected in the fall, the FBI said, though we must note though the FBI’s numbers are invariably incomplete. Eric H. Holder Jr., who recently stepped down as attorney general, said this year that since not all police agencies report how many officers are killed, there is an “unacceptable” lack of data regarding these episodes or times police officers use lethal force.

Still, this new FBI report comes just days after two Mississippi police officers were shot and killed during a traffic stop over the weekend, which occurred not long after the funeral for a New York City police officer who was shot and killed while making a stop in Queens last week.

The FBI provided relatively few details about the deaths last year, but the information they did release allowed for a snapshot of some of the circumstances.

Almost all of the officers killed last year were shot, the FBI said. One officer was killed with his own weapon. Eight of the officers were killed in what the FBI referred to as ambushes, while many of the others were killed responding to disturbances, making traffic stops or investigating people. And two out of three officers killed last year were wearing body armor at the time.

There were also 44 officers who died in what the FBI referred to as accidental deaths, which included more than two dozen car accidents, two inadvertent shootings and, in one case, an officer who drowned.

News that the number of deaths jumped back up last year arrives at a particularly tense moment between police and the communities they serve.

Months of protests over how police officers use lethal force have erupted across the country after deaths in Ferguson, Mo., Cleveland, New York City and, most recently, Baltimore. Some police officers have said they feel unfairly besieged by the protests, a sentiment that bubbled to the fore after two New York City police officers were gunned down in their squad car last December.

So far this year, 10 officers were killed after being shot by suspects, according to the Officer Down Memorial Page, which tracks law enforcement deaths. There were also two officers inadvertently shot and killed during training exercises, while other officers died in traffic-related accidents, including some who were responding to calls or other traffic accidents.

The first officer believed to be shot and killed by a suspect this year was Terence Green, a Georgia officer who died in March in what authorities called an ambush. A day later, Robert Wilson III, a Philadelphia police officer, was shot and killed when he stopped in a video game store to buy a gift for his son and happened upon a robbery he tried to stop.

Benjamin Deen and Liquori Tate, the two officers killed in Hattiesburg, appeared to be the 9th and 10th officers shot and killed by a suspect this year.

“The shocking assault on law enforcement officers in Hattiesburg, Mississippi, struck at the heart of that great city,” Attorney General Loretta Lynch said in a statement Monday. “The Department of Justice stands ready to offer any possible aid to the Hattiesburg community as they investigate this appalling incident. And we will continue to do all that we can to protect our officers across the country and support all those who wear the badge.”