An attempted car theft escalated into a fight early Tuesday morning; a man tried to stop the alleged prowler, who died in the scuffle, police said.

A man at the scene told KGW his son came outside and spotted someone trying to break into his fiance's vehicle, so he lunged at the suspect and the two fought.

A witness said he heard someone yell "drop the knife," but he was unsure if there even was a knife. Sgt. Brian Schmautz with the Portland Police Bureau said no one was stabbed.

At some time during the fight, one of the men stopped moving, witnesses said.

Brian Walter Perry, 35, was soon taken to a local hospital where he was pronounced dead.

A medical examiner completed an autopsy Tuesday, but police said the cause of death was undetermined.

No one has been charged in connection with the investigation and no arrests are expected, according to Schmautz.

Homicide detectives joined the investigation and the man who confronted the alleged prowler was detained for questioning. His father told KGW he had some cuts and scratches, but no serious injuries.

The incident happened around 5 a.m., in the 300-block of Hayden Bay Drive.

(KGW reporter Mike Benner also contributed to this article.)