Outrage is brewing over a police shooting in Idaho … video shows a group of officers shooting a teen armed with a knife, but the boy’s family says he’s nonverbal, autistic and suffers from cerebral palsy.

The incident happened in Pocatello … with cops shooting 17-year-old Victor Perez 9 times in the yard outside his home, leaving him in critical condition … according to the Associated Press, which also reports Perez had to have a leg amputated.

Video of the Saturday shooting went viral … sparking protests outside Pocatello PD. Folks say they’re questioning why the 4 officers who responded to the scene appeared to be trigger-happy and didn’t make much of an effort to de-escalate the situation before unleashing a hail of bullets.

The teen’s aunt told KIFI-TV police didn’t ask what was going on when they arrived … and she says Victor can hardly walk and has the brain of a 5-year-old.

Cops say they responded after getting a 911 call reporting a domestic disturbance involving a person wielding a knife who appeared to be intoxicated. The boy’s family says he was NOT intoxicated and staggers when he walks due to his cerebral palsy.

Based on the video, it only took about 12 seconds for police to shoot Perez after they got to his family’s home.

Pocatello Police Chief Roger Schei says officers make decisions in seconds and assess threats. He says in this shooting, “two individuals were within a few feet of an armed, noncompliant individual. The risk was immediate, and the situation rapidly evolving.”