Vancouver police spokesman Sgt. Randy Fincham said the attack happened at around 7:30 p.m. PT. He said the attacker and the victim did not know each other.
A witness who saw the attack rushed to intervene, and managed to disarm the man with the knife.
Fincham said that when police got to the park, officers saw that the suspect had a second knife. The suspect wasn't following the officers' instructions, and a police dog was used to bring the suspect under control.
A 45-year-old Vancouver man was arrested for attempted murder and possession of a dangerous weapon.
Fincham said the victim, a 50-year-old Vancouver man, was taken to the hospital with slash wounds on his head and a hand, but his injuries were not thought to be life-threatening.
Fincham said the witness who intervened may have saved the victim's life.
“If not for the actions of this Good Samaritan, the victim could easily have suffered injuries beyond the slash wounds," he said.