Videos of officer-involved shootings, whether captured on a smartphone and shared through social media or released by police departments amid public pressure, have this year continued to ignite national protests over the use of lethal force against U.S. minority communities. This year and especially in recent months, a spate of officer-involved killings were accompanied by videos that showed suspects, both armed and unarmed, gunned down even after they appeared to surrender or be subdued.

A year and a half after the emergence of Black Lives Matter, a national anti-police brutality movement, some police officials have been quick to provide answers to the public after fatal shootings. But swift transparency has not been accompanied by widespread changes to use-of-force policies, activists said, evidenced by the most recent fatal police encounters.

However, it took more than a year for officials in Chicago to release video of the 2014 police shooting death of Laquan McDonald, a 17-year-old African-American shot 16 times by a city officer now charged with murder. Within the span of a week last month, Mayor Rahm Emanuel apologized for the lack of transparency, replaced the police superintendent, formed a new police oversight task force and welcomed a federal Department of Justice investigation.

Separately, the prosecutor's office in Cook County, Illinois, announced last week that it would not charge the Chicago police officer who fatally wounded Ronald Johnson, a 25-year-old African-American shot as he ran from police into a public park in 2014. Authorities said Johnson had brandished a weapon, although his family has alleged a cover-up.

Newer Videos Emerge

Los Angeles County Sheriff's Department announced Sunday it planned to investigate the fatal shooting of Nicholas Robertson, a 28-year-old African-American man, after a video of the incident emerged. Robertson was killed Saturday outside of a shopping area in Lynwood, California, by two officers whom he pointed a weapon at, authorities said. The sheriff’s deputies fired 33 shots at Robertson, who is seen on the video trying to crawl away from the officers.

Warning: The video below and the language in it are extremely graphic in nature.

Protests continued over the weekend behind the Dec. 2 shooting death of Mario Woods in San Francisco. Video of the incident conflicts with authorities' initial claim that five officers shot the African-American man in self-defense. Authorities said Woods, 26, had a knife at the time of the shooting, according to media reports. Amid anger among local students and members of the predominantly black Bayview neighborhood, where Woods was shot, San Francisco Police Chief Greg Suhr said officers should be equipped with fewer lethal Taser guns. Mayor Ed Lee called for reforms of officers' use-of-force policy.

Warning: The video below and the language in it are extremely graphic in nature.

An August police shooting in Bexar County, Texas, also sparked new outrage last week, after authorities released a video showing the death of Gilbert Flores. Investigators have said Flores, a 41-year-old Hispanic man, was in possession of a knife. A grand jury last week voted not to indict the deputies who were involved in the shooting, the New York Daily News reported.

The new video shows Flores with his hands in the air before he was killed. Although police had been responding to a domestic abuse call before the shooting, Flores’ family has filed a civil lawsuit against the sheriff’s department.

Warning: The video below and the language in it are extremely graphic in nature.

Other videos that emerged or were released by officials after police shootings include the July case of Sam Dubose in Cincinnati, Ohio, and Walter Scott's case from April, in North Charleston, South Carolina. Officers involved in those cases have been indicted on charges that include murder, manslaughter and official misconduct.