Story highlights Superintendent Eddie Johnson says he has concerns about Wednesday's shooting

Unidentified officer says Kajuan Raye was armed but no gun has been found

(CNN) A Chicago police officer who said he shot and killed a black man this week after the teenager pointed a gun at him has been relieved of his police powers, the Chicago Police Department said Saturday.

The sergeant involved in the shooting told investigators that Kajuan Raye, 19, twice pointed a weapon at him, but no gun has been found in the evidence gathering, the department said.

"Based on the little information we know at this point, I have concerns about this incident," police Superintendent Eddie Johnson said.

Johnson said that a preliminary report from the medical examiner's office, which determined Raye had been shot in the back, also figured into his decision to take the officer's gun and badge away.

The city's Independent Police Review Authority is investigating the shooting. Police have not released the sergeant's name.