The Oklahoma County district attorney has cleared a police officer in the shooting death of a homeless man on a city street.

The Oklahoman reports (http://bit.ly/29WDqEB ) that District Attorney David Prater wrote that Sgt. Steve Helmer had "no viable option" but to shoot Derek Prophet on May 25.

Police say Prophet was among a group of homeless men loitering near an intersection and that Helmer and another officer told the group to take their belongings and move along, but Prophet refused.

A grainy video of the shooting from a nearby restaurant shows Prophet then lunged at Helmer and the officer shot him. Prophet then stepped away before collapsing and dying.

Police say Prophet had a knife in his hand.