An autistic, non-verbal teenage boy who was shot repeatedly by US police from the other side of a chain link fence while he was holding died on Saturday (local time) after being removed from life support, his family said.

Victor Perez, 17, who also had cerebral palsy, had been in a coma since the April 5 shooting, and tests on Friday showed that he had no brain activity, his aunt, Ana Vazquez, told The Associated Press.

He had undergone several surgeries, with doctors removing nine bullets and amputating his leg.

Police in the south-west Idaho city of Pocatello responded to a 911 call reporting that an apparently intoxicated man with a knife was chasing someone in a yard.

It turned out to be Perez, who was not intoxicated but walked with a staggered gait due to his disabilities, Vazquez said.

His family members had been trying to get the large kitchen knife away from him.

Video taken by a neighbour showed that Perez was lying in the yard after falling over when four officers arrived and rushed to the fence at the edge of the yard.

They immediately ordered Perez to drop the knife, but instead he stood and began stumbling toward them.

Officers opened fire within about 12 seconds of getting out of their patrol cars and made no apparent effort to de-escalate the situation.

The shooting outraged Perez’s family and Pocatello residents, and a vigil had been planned for Saturday morning outside the Pocatello hospital where he was treated.

“Everybody was trying to tell the police, no, no,” Vazquez said. “Those four officers didn’t care. They didn’t ask what was happening, what was the situation.”

“How’s he going to jump the fence when he can barely walk?” she said.

The officers, whose names have not been released, were placed on administrative leave.

Decisions about whether charges should be filed against them will be made after an independent investigation by the Eastern Idaho Critical Incident Team, Bannock County Prosecutor Ian Johnson told the AP via email.

“When that investigation is complete a report will be submitted for review,” he said. “In a continued effort to ensure independent and objective consideration, said report will be reviewed by an agency outside of Bannock County.”

Pocatello Mayor Brian Blad said in a statement on Friday, after the family announced that Perez had no brain activity, that officials’ thoughts and prayers were with them.

“We recognise the pain and grief this incident has caused in our community,” Blad said.

Blad said on Thursday that the city was “addressing this matter with the seriousness and thoroughness it deserves and with the appropriate respect for the gravity of the situation.”

“The criminal, external, and internal investigations regarding the officer-involved shooting are underway, which is why we cannot answer questions out of concern of interfering with or compromising the investigation,” he said.