A timeline of police killings in the U.S. and its territories

In this Jan. 7, 1973, file photo, a plainclothes police officer runs for cover as he moves into the area of the burning Howard Johnson Hotel in New Orleans. (AP / File)

Authorities said Monday that police officers were clearly targeted and ambushed in this weekend's shooting in Baton Rouge, Louisiana, which killed three officers and wounded three others. It's the latest such ambush in the United States, and happened just 10 days after five police officers in Dallas were gunned down.

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July 7: A gunman in Dallas opened fire on police officers working at a protest about recent killings by police of black men in Minnesota and Louisiana. The attacker, Micah Johnson, killed five officers and wounded nine others and two civilians before police killed him with a robot-delivered bomb when negotiations failed. Authorities say Johnson, who was black, told negotiators he wanted to kill as many white police officers as he could. It was the deadliest day for American law enforcement since September 11, 2001.

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Dec 28, 2015: Officer Guarionex Candelario Rivera showed up unannounced at his police station in Ponce, Puerto Rico, and fatally shot three fellow officers. Candelario, a 19-year police veteran, killed Lt. Luz Soto Segarra, Cmdr. Frank Roman Rodriguez and policewoman Rosario Hernandez De Hoyos. Candelario was shot twice but survived.

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May 9, 2015: Two Hattiesburg, Mississippi, police officers, Benjamin Deen and Liquori Tate, were shot to death during a traffic stop. Three suspects were later arrested.

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Dec 20, 2014: Two New York City police officers, Wenjian Liu and Rafael Ramos, were ambushed and shot to death in their vehicle without warning by a man who approached the passenger window of their marked police car. The suspect, 28-year-old Ismaaiyl Brinsley, then fatally shot himself. Brinsley was black; the officers were Asian and Hispanic, police said. The shooting came amid heightened tensions between law enforcement and minority communities.

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September 12, 2014: A survivalist ambushed two Pennsylvania state troopers outside of a police barracks late at night, killing Cpl. Bryon Dickson and wounding Trooper Alex Douglass. Suspect Eric Frein led authorities on a 48-day manhunt through the heavily wooded Pocono Mountains before U.S. marshals captured him at an abandoned airplane hangar. He has pleaded not guilty.

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June 8, 2014: A man and a woman ambushed two police officers eating lunch at a Las Vegas pizza restaurant, fatally shooting them before fleeing to a nearby Wal-Mart where they killed a third person and then themselves in an apparent suicide pact. Officers Alyn Beck and Igor Soldo died.

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Aug. 28, 2010: Two police officers were ambushed in a tiny Alaskan village of Hoonah before a SWAT team and dozens of other law officers surrounded a house where the gunman took refuge. Officers Tony Wallace and Matt Tokuoka died after the shooting. Hoonah resident John Marvin Jr. was captured and charged in the deaths.

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May 20, 2010: Two West Memphis, Arkansas, police officers doing anti-drug work were shot to death by two men wielding AK-47s along a busy Arkansas interstate. Sgt. Brandon Paudert and Officer Bill Evans died at a nearby hospital. The suspects were later killed in a shootout that injured the local sheriff and a deputy at a crowded Wal-Mart parking lot.

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Nov. 29, 2009: Four police officers were shot and killed in an ambush in a coffee shop in Lakewood, Washington, by ex-convict Maurice Clemmons. Killed were officers Mark Renninger, Ronald Owens, Tina Griswold and Greg Richards. Clemmons was shot and killed by police after a two-day manhunt.

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Jan. 13, 1998 -- University of Nevada, Reno Police Sgt. George Sullivan is ambushed and attacked with a hatchet while doing paperwork in his squad car. Siaosi Vanisi is later convicted and sentenced to death for Sullivan's slaying. Witnesses testified at Vanisi's trial that he stalked Sullivan after repeatedly telling friends and relatives that he wanted to kill a police officer.

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Dec. 31, 1972, and Jan. 7, 1973: Mark James Essex, a member of the Black Panthers who was discharged from the Navy for going AWOL, kills nine people in New Orleans, including five police officers, in two sniper attacks. Essex is shot more than 200 times by police sharpshooters on Jan. 7. Authorities find the walls of his apartment covered in anti-white graffiti.

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April 6, 1970: Career criminals Bobby Davis and Jack Twinning kill four California state troopers in a four-minute gunbattle in Los Angeles County. Twinning kills himself when authorities surround a house where he is holding a hostage; Davis is soon arrested and, almost three decades later, kills himself at Kern State Prison.

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Oct. 30, 1950: Members of a nationalist party seeking to overthrow the government of Puerto Rico shoot and kill eight police officers in San Juan, including Chief Aurelio Miranda-Rivera. The revolt is put down by the U.S. military, the FBI and the CIA.

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Jan. 2, 1932: Six officers from two Missouri agencies are killed as they surround a house where two suspects wanted in the murder of a Greene County marshal are holed up. The suspects flee to Texas and kill themselves when authorities track them down.