Nationwide, 126 law enforcement officers died in the line of duty in 2014, including 50 officers killed by firearms, according to an annual report released Tuesday.
The 2014 figures represent a jump from last year's historically low tallies, when 102 officers died, including 32 by firearms, but remain below the previous decade's average, according to the report from the National Law Enforcement Officers Memorial Fund.
On average, 166 officers died in the line of duty, including 57 killed by firearms, in the first decade of the millennium, said Craig W. Floyd, the fund's chairman.
After firearm deaths, the second-leading cause of death in 2014 was traffic-related incidents, the report said, taking the lives of 49 officers.
California, the nation's most populous state, led the country in officer fatalities with 14, according to the report. Texas saw 11 officers die in the line of duty, and New York had nine, which includes two officers assassinated as they sat in their squad car this month.
Floyd said he was alarmed by the 15 officer deaths that came as a result of ambushed attacks with a firearm, which matches 2012 as the most ambush attacks in a single year since 1995.
Floyd was particularly worried that more shooters could be inspired by high-profile killings including those motivated by anti-government or anti-police sentiment. He noted the ambush killing of two Las Vegas officers at a pizza shop in June; the September shooting of two Pennsylvania state troopers, one of whom died; and the slayinng of the two New York police officers Dec. 20.
"We are worried that the types of criminals the officers are having to confront are more brazen and cold-blooded than ever before," he said.
Though police shootings jumped this year, they have been on the decline for decades, according to the report and law enforcement experts. The average number of officers shot and killed has decreased from 127 per year in the 1970s, to 87 in the 1980s, 68 in the 1990s, and 57 in the 2000s, according to the report.
The drop in deaths coincides with an increasing number of officers wearing soft-body armor, departments establishing specialized SWAT teams, and faster medical response times, said William Terrill, a criminal justice professor at Michigan State University.
Those advances have led to a small number of police deaths relative to the number of sworn officers in the country, which Terrill estimates at 800,000.
Terrill said he feared the uptick of shootings and ambushes in 2014 could further ingrain an "us versus them" mentality among some police officers. "Police officers will be more apt to be more suspicious of citizens and that may cause them to be more aggressive," he said.
Terrill said that as officer deaths have been on the decline, shootings by police officers have been on the rise, according to data voluntarily submitted by local police agencies to the Federal Bureau of Investigation's Uniform Crime Reporting Program.
There were 461 justifiable homicides by law enforcement officers in 2013, according to the data, up from the mid to high 300s during the 2000s. But the data are incomplete because departments volunteer the information, Terrill said, and the actual number of police shootings is likely much higher.
The report comes in a year where tensions have continued to grow in major cities between police and residents.
This month, New York police officers Rafael Ramos and Wenjian Liu were killed in an ambush by a man who threatened to avenge the killings of unarmed black men Michael Brown in Missouri and Eric Garner in New York. The gunman then killed himself, police said.