In forested parkland above downtown Portland, an officer has killed an unidentified man who was coming at him with a knife, police said Tuesday.

PORTLAND — In forested parkland above downtown Portland, an officer has killed an unidentified man who was coming at him with a knife, police said Tuesday.

A day after the shooting, the man's identity was a mystery. He was thought to be a transient, and authorities said he cut his neck many times before he was taken down by four rounds from the officer.

The man, who was white, had no identification but appeared to be in his 60s, said Dr. Karen Gunson, the state's chief medical examiner.

The age estimate could be off by many years, she said.

"We don't have an idea who he might be," Gunson said Tuesday. "We don't even have a clue."

Police Chief Rosie Sizer said Officer Jason Walters, a 13-year veteran, went to the Hoyt Arboretum Monday afternoon to investigate a report that a man was threatening people.

Near a bathroom, Walters found a man with blood on his hands, neck and face and a knife in his hand, Chief Rosie Sizer said.

The officer retreated but shot the man when he continued to advance, Sizer said.

Gunson said the man had "multiple, multiple" shallow, self-inflicted wounds in his neck. He died of a gunshot wound to the hip that severed a major artery, she said. He was also hit in the torso and the arms, Gunson said.

The arboretum is within more than 5,000 acres of forest atop the mountains on Portland's west side. It is amid attractions such as the Oregon Zoo and the Portland Japanese Garden. Nearby trails attract thousands of city dwellers seeking retreat and exercise. Its shelter is a venue for weddings and picnics.

"I'm glad that Officer Walters was there to protect the community in a location that is deeply loved and often visited," Sizer said.

Sizer appeared at a press briefing Tuesday but didn't take questions. The bureau's spokeswoman, Detective Mary Wheat, said the case would go before a grand jury as part of standard operating procedure.

Gunson said police are trying to identify the man through fingerprints.

The knife was like a razor-sharp hobby knife and had a 6-inch handle, Wheat said. She wouldn't say how close the man got to the officer.

The city's Police Bureau has been under scrutiny in recent years for fatalities, including the 2006 death of a mentally ill man who died after he was tackled during an arrest and most recently in January when an officer shot an unarmed man in the back.