(CBS) — State Police are conducting an independent investigation after a DuPage County Sheriff’s Deputy shot and killed a teenager early yesterday near Villa Park.

The deputy was responding to a domestic violence call at a home near Standish Lane and Ardmore Avenue.

There was an altercation, police said, between the deputy and a teenager identified as Travon Johnson.

The deputy, who was the only officer at the scene, said he thought the teen had a knife, and he fired multiple shots, killing Johnson.

The teen reportedly had mental issues and the Daily Herald reports it was the first deadly shooting invoving a DuPage sheriff’s deputy in more than 20 years.