A 15-year-old autistic boy was shot dead by Chicago police who were called by his parents after he refused to go to school.

Stephon Watts, who suffers from Aspergers Syndrome and a form of attention deficit disorder, allegedly threatened officers with a kitchen knife.

The boy's parents called police to their home in Calumet city on Wednesday for help restraining him when he became aggressive after refusing to go to school.

His mother Danelene Powell-Watts claimed he was only holding a butter knife when he threatened officers, who opened fire.

Police had been called to the home at least 10 times before to help Stephon's parents restrain him. His mother claimed they could have used a stun gun to subdue him.

She screamed abuse at police as they gave a press conference into the tragic shooting at Calumet City police station.

"They shot my son," she yelled from outside the station, CBS Chicago reported. "Every last one of you knows my son has autism."

She told CBS reporters: "They didn't have to murder him. This is nothing but murder and they shoot to kill."She claimed Stephon was holding a butter knife.

Calumet City police chief Edward Gilmore said officers did "everything they possibly could" to avoid the use of lethal force.

"It's unfortunate that we had to get to this situation," he said.

"We tried to do everything we could to keep him from being a victim, as he was an offender. He chose to be an offender."

He said that the lead officer didn't have a stun gun and that Stephon lunged at an officer with a knife.

"Unfortunately when he slashed the officer's arm, the officer felt his life was in jeopardy and he had nothing else to do but defend himself"

The two officers who entered the house have been placed on administrative leave.