Newly released video shows a Fresno, California, police officer shooting a fleeing, unarmed 16-year-old in the back of the head and then handcuffing the boy as he lies motionless on the ground.

Surveillance footage of the 14 April 2017 killing of Isiah Murrietta-Golding, released this week by the family’s attorney, has spread across the US, with critics calling it another example of extreme police brutality and unjustified lethal force that would have received little attention if lawyers hadn’t published the video.

The footage shows the teenager running from officers, jumping a fence, falling to the ground and continuing to flee. Murrietta-Golding was an estimated 35 feet away from the officers when one of them fired a single bullet into his head. The officer then hopped the fence, approached the boy’s limp body and handcuffed his hands behind his back.

The video comes after the police department in Fresno, a city in California’s Central Valley, refused to release the footage while publicly stating that the killing was “justified”, said Stuart Chandler, an attorney for Murrietta-Golding’s father.

“The city was so adamant that the officer ‘feared for his life’,” the lawyer told the Guardian on Thursday. “Why were they hiding the video? If a picture speaks a thousand words, then the video speaks a million words.”

The aftermath of the shooting caught on video was especially upsetting to watch, the attorney added.

“He’s unconscious and in the process of dying. What is the threat?” said Chandler. “They just saw him as an animal who had been shot. They hunted a target. It’s inhumane.”

A paramedic report showed that police declined to remove the handcuffs when an EMT arrived, with an officer saying police would only take them off later at the hospital.

Jerry Dyer, the Fresno police chief at the time of the shooting, has previously stated that the officer, Sgt Ray Villalvazo, thought “he was about to be shot”. Dyer claimed the teen “reached into his waistband several times”, according to the Fresno Bee. But the new footage, which Chandler obtained in the process of a civil lawsuit against the department, only shows him running away as he appears to be holding up his pants. He was unarmed.

Fresno’s current police chief, Andrew Hall, continued to defend the shooting as a justified use of deadly force in a statement this week, saying Murrietta-Golding was “known to carry firearms” and noting that he had entered a daycare center when he hopped the fence.

Footage of California police killing unarmed teen prompts claim of 'trigger-happy' officers Read more

Hall further alleged that Murrietta-Golding was involved in a crime the previous day.

A spokesperson for the Fresno police department did not respond to an inquiry seeking clarification on the firearms allegation and the use of handcuffs.

According to the family’s suit, police were trying to question Murrietta-Golding, but lacked a search or arrest warrant, so officers staked out his house then pulled him over in a car with two other teens and “held them at gunpoint”. At that point, he fled.

Lawyers for the family noted that the shooting happened on a Saturday while the daycare center was empty. And Chandler said it was “despicable” that police were still trying to attack Murrietta-Golding’s character, saying the allegations and insinuations about what had happened prior were not relevant to the officer’s decision to kill the boy as he fled.

The shooting happened nine months after Fresno police killed Dylan Noble, shooting the unarmed 19-year-old multiple times, including while he was lying on the ground, barely moving. Advocates have long argued that Fresno police need to focus on de-escalation and anti-bias training, and a 2017 American Civil Liberties Union report found that police shoot people of color at a hugely disproportionate rate in the city.

Chandler faulted Fresno police for failing to implement meaningful reforms after both killings of unarmed teens.

“There has been no change in either the culture, the training or the mentality regarding the use of deadly force.”

The state of California recently passed a major reform meant to limit the use of lethal force by police, with a law considered the strictest in the country.