Hamilton police say a man is in serious condition with head injuries after he collided an HSR bus early Thursday morning and struck his head on a sidewalk.

Police have two lanes of Main Street at Locke St. shut down for investigation.

Paramedics were called at 12:30 a.m. for reports of a pedestrian struck by a bus.

Staff Sgt. Frank Miscione said a 35-year-old man was just west of Locke on Main when the eastbound bus in the south curb lane came by and the man ran at the bus with 'full force.'

Police say the man then struck his head on the sidewalk in the fall.

There were no passengers on board at the time.

The police Collision Reconstruction Unit is investigating. Police say it's unclear right now if drugs, alcohol or mental health are factors.

Police expect the lanes will be closed on Main for some time Thursday morning.