Boston ? Two registered sex offenders were fatally shot in their central Maine homes early Sunday, and a Canadian man sought in connection with the slayings shot himself after Boston police cornered him on a bus, Maine authorities said.

Stephen A. Marshall, 20, shot himself in the head with a .45 caliber handgun when officers stopped the bus he was on and climbed aboard, said David Procopio, spokesman for the Suffolk district attorney.

Marshall was rushed to Boston Medical Center where he was in critical condition late Sunday night with severe brain damage, Procopio said.

No one else on the bus was injured, Procopio said, but five passengers who were splattered with blood were taken to area hospitals to be examined.

Maine State Police alerted Boston authorities that Marshall could be heading to the city, about 250 miles south, after Marshall’s pickup truck was found abandoned. Police discovered bullets linked to him in the bathroom at a bus station in Bangor, Maine.

The shootings of Joseph L. Gray, 57, of Milo, Maine, and William Elliott, 24, of Corinth, Maine, led state police to take down the Maine Sex Offender Registry Web site as a precaution, state Department of Public Safety spokesman Stephen McCausland said. The site lists the photos, names and addresses of more than 2,200 sex offenders.

It was not immediately clear if or how Marshall knew either Gray or Elliott.