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The number of law enforcement officers shot to death in the line of duty is up by more than 50% this year, and the leading circumstance of those shootings were ambush-style attacks.

That’s according to the nonprofit Washington-based National Law Enforcement Officers Memorial Fund which released its findings Tuesday.

There were 50 officers killed by firearm in 2014, up from 32 the previous year. Of those 50 officers, 15 were killed in ambush attacks, the Memorial Fund said.

Ten were killed ambush-style attacks in 2013, the Fund said.

The FBI, however, found that five officers were ambushed and killed in 2013.

According to the Fund’s 2014 report, 126 federal, state, local, tribal and territorial officers were killed in the line of duty in 2014, compared to 102 in 2013.

CNN has not analyzed each case and cannot authenticate the group’s findings.

The report comes amid simmering distrust and tension between the police and some communities across the country. It was also published less than two weeks after the December 20 ambush shooting of two New York City police officers.

Ismaaiyl Brinsley, 28, approached Officers Wenjian Liu and Rafael Ramos as they sat in their marked patrol car in Brooklyn on December 20 and shot them to death.

The Memorial Fund evoked Liu and Ramos’ deaths in a statement Tuesday.

“With the increasing number of ambush-style attacks against our officers, I am deeply concerned that a growing anti-government sentiment in America is influencing weak-minded individuals to launch violent assaults against the men and women working to enforce our laws and keep our nation safe,” said Fund Chairman and CEO Craig W. Floyd. “Enough is enough. We need to tone down the rhetoric and rally in support of law enforcement and against lawlessness.”

The rhetoric Floyd is referring to isn’t confined to the angry words and sometimes violent clashes between police and protesters after Michael Brown was shot to death in Ferguson, Missouri, or the death of Eric Garner after police attempted to subdue him, which also spurred national protests, said Fund spokesman Steve Groeninger.

Groeninger told CNN that the uptick in ambush-style attacks were “punctuated” by the New York officers’ slayings, but there were other targeted attacks against law enforcement in 2014 that concern the Fund.

They include:

— In Las Vegas in June Jerad Miller and his wife surprised two police officers as they ate lunch, shooting them to death. Witnesses said the Millers placed a “Don’t Tread on Me” flag and a Nazi swastika on one officer’s body.

— In Jersey City, New Jersey, in July, police said a man assaulted a Walgreens security guard, and took his gun in order to carry out the ambush-style killing of an officer, according to the Jersey Journal.

— In September, two Pennsylvania State Police troopers were ambushed and shot outside the police barracks in Blooming Grove. The hunt for the alleged killer, Eric Frein, lasted for almost seven weeks. He was captured at an abandoned airport on October 30. Frein was hit with terrorism charges in November for allegedly admitting that he shot the officers to change the government and “wake people up.”