Within seconds of arriving on the scene, police officers in eastern Idaho shot a teenager whose family says he is nonverbal and autistic as he stepped toward authorities with a knife from behind a chain-link fence, a witness’s video shows.

Officers shot the 17-year-old, identified by his family to the Associated Press as Victor Perez, nine times outside his home in Pocatello, leaving him in critical condition and with one of his legs amputated, they said. The shooting Saturday prompted protests outside the Pocatello Police Department, with many locals questioning on social media why the four officers appeared to make no effort to de-escalate the situation before resorting to lethal force.