A 25-year-old man attacked a 63-year-old man early Sunday at the Bellevue Transit Center, according to the Bellevue Police Department.

The 63-year-old was severely beaten, critically injured and taken to Harborview Medical Center, said Meeghan Black, spokesperson for the police department. Officers do not yet know what motivated the attack, but it appears to be isolated, she added.

A witness waiting for a ride reported the assault to police. Police and paramedics arrived within minutes and treated the 63-year-old on site before taking him to the hospital.

Officers found the 25-year-old two hours after the attack, which happened shortly after midnight, a news release from the department said. They arrested him near an overpass a few blocks from the Bellevue bus station, at 10850 N.E. Sixth Street, Black said.

They closed the transit center briefly during the investigation. It has since reopened.