A motorcyclist is accused of fleeing a crash in the Twin Cities that left his sister with "serious permanent disfigurement," charges state.

The 70-year-old man from Inver Grove Heights, Minnesota, is charged with one count of criminal vehicular operation, court documents filed Tuesday in Washington County show.

The crash happened just before 7 p.m. Sunday on Highway 61 at 70th Street in St. Paul Park, the Minnesota State Patrol said.

First responders found a woman "alive but with a severe head injury" and took her to Regions Hospital, the complaint states. As of Tuesday, she remains in critical condition.

A witness told investigators he was going about 80 mph when a motorcyclist passed him and gave him the middle finger. The motorcyclist then hit another vehicle's bumper, the witness said, which caused the woman to be thrown off the bike.

The witness's dashcam and Minnesota Department of Transportation cameras show the suspect stop at the next off ramp, "look back at the accident scene" and keep driving, according to the complaint.

Officers identified the motorcyclist via the license plate and went to his home. As he was showing the officers his motorcycle, the complaint states he unpromptedly asked, "Is my sister OK?" 

He allegedly told police he "knew [she] fell off the back but got scared and kept driving." He also told police he and his sister were coming back from a bar in Wisconsin when the crash occurred and that he had been drinking before it happened, according to the complaint.

The man showed signs of impairment during a field sobriety test, investigators said, and a breath test placed his blood alcohol content at .127, though he told police he drank more after the crash. Results of a blood test are pending.

The man is in custody.