Firearms-related deaths of law enforcement officials in the US increased 56 percent in 2014 over the prior year, the National Law Enforcement Officers Memorial Fund has concluded. About one-third of the deaths were a result of an ambush, the fund said.

The 2014 Law Enforcement Officer Fatalities Report [PDF] said 50 officers were killed by guns in 2014 compared to 32 the year before. Fifteen were killed by ambush, according to the report.

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The increase comes amid a flurry of anti-police sentiment following the Michael Brown shooting in Ferguson, Missouri and the choke-hold death of Eric Garner by the New York Police Department. Garner's arrest was captured on video, and it was among one of dozens of clips featuring police misconduct to widely circulate on the Internet in 2014.

"We've been talking about this well before the Michael Brown and Eric Garner incidents, and the protests over those particular cases—that there has been a very prevalent anti-government sentiment in this country for some time now, and I do believe that anti-government sentiment can influence weak-minded individuals to commit violent acts against law-enforcement officers," Craig Floyd, the memorial fund's chairman, said in a statement.

Floyd added: "That's at least part of the reason we're seeing this increase in ambush-style attacks, officers being targeted simply because they're cops in uniform."

Gun-related deaths of officers remain below historic highs, and 2014 was lower than the average yearly figures for the past decade, the report said.

Overall, as many as 126 officers were killed in the line of duty in 2014. That's a 24 percent increase from the prior year when 102 officers were killed. While firearms were the leading cause of death last year, traffic-related incidents were the second-leading cause—killing 49 officers. That's an 11 percent increase over the year prior, when 44 officers died from traffic-related causes, the report said.