PORTLAND, Ore. - A grand jury has cleared a Portland police officer who used deadly force last month against a man who was armed with a utility knife.

The Multnomah County District Attorney's Office said Friday the grand jury found Officer Samson Ajir used a "lawful exercise of self-defense" in the fatal shooting of 24-year-old Terrell Johnson.

Officers responded May 10 after a 911 caller reported that a man was acting erratically and threatening people at a light-rail station. An arriving officer spoke with Johnson but he was non-compliant and would not sit down, police said.

As Ajir and his brother, Clackamas County Deputy AJ Ajir, arrived on the scene, Johnson ran off.

Officer Samson Ajir tracked Johnson down and Johnson turned toward him while displaying a utility knife, police said. Ajir fired his handgun multiple times.

Additional officers rendered medical aid but Johnson died at the scene.

Johnson's family told police he had been struggling with drug addiction, which may have affected his mental health.

Transcripts of grand jury testimony will likely be released to the public sometime in July on the police bureau's officer-involved shooting and custody death web page.

Police said Ajir is an eight-year veteran of the police bureau and was assigned to the Transit Police Division when he shot and killed Johnson. The bureau is also conducting an internal review of the incident.

Background: Man killed by Portland officer was armed with knife, police say