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A Memphis, Tennessee, police officer makes a pencil rubbing from the memorial wall at the National Law Enforcement Officers Memorial in Washington, D.C., May 15, 2009. Getty Images/Chip Somodevilla

As anti-police brutality protesters prepared this weekend to mark the one-year anniversary of nationwide demonstrations sparked by a string of officer-involved deaths, the law enforcement community said it hoped to shift some attention to the increased number of line-of-duty deaths that have occurred in 2015. Even with relations between police and local communities strained by protests since last summer, the number of officers who have died because they were shot by suspects -- 18 nationwide so far this year -- has dropped compared to last year.

However, an increase in officer deaths overall can be attributed to traffic accidents, according to several nonprofit groups that track reports of fallen officers. Traffic accidents have been the leading cause of death for police officers so far in 2015, the National Law Enforcement Officers Memorial Fund said in its midyear report.

Spokesmen for police groups have said officers feel their safety has been threatened by the “Black Lives Matter” protests. But they also said that declines over the last decade in community policing -- or the embedding of officers on foot patrols in neighborhoods with high crime rates -- has meant more officers are required to conduct their jobs in squad cars where they are subject to increased traffic risks.

Still, the loss of officers killed by suspects were the gravest concern for police officers' groups. Through the first half of 2015, 16 police officers were shot and killed. As of Wednesday, that number had climbed to 18. That's still down from 27 officers killed during the same period in 2014, the Washington Post reported.

Officer Sean Bolton, 33, of the Memphis (Tennessee) Police Department, who was killed over the weekend, was the 18th police officer killed in the U.S. this year. Bolton had served in the U.S. Marine Corps in Iraq and joined the Memphis police force in 2010, the Post reported.

“We lost not only an officer, but a great man, a dedicated servant to our community, and a family member,” Memphis Police Director Toney C. Armstrong said in a statement about Bolton’s Aug. 1 death.

Authorities said they had arrested 29-year-old Tremaine Wilbourn, who turned himself in for Bolton’s death following a manhunt that began over the weekend. Wilbourn, who police say shot Bolton multiple times after the officer approached his illegally parked vehicle, was expected make his first appearance in court Wednesday morning.

Number of People Killed by Police by State in 2015 | FindTheBest