Maine police found two registered sex offenders shot to death in towns 25 miles apart and quickly zeroed in on a suspect.

After almost 12 hours and a manhunt that stretched through three states, police pulled over a bus carrying Stephen A. Marshall to Boston and the 20-year-old Canadian fatally shot himself as officers boarded.

Marshall died late Sunday before he could answer questions about whether he knew the Maine victims -- sex offenders whose deaths prompted officials to take down the Maine Sex Offender Registry Web site. The site lists the photos, names and addresses of more than 2,200 sex offenders.

"We will try to establish what is the link between these three men but as of tonight there's no known connection," Maine Department of Public Safety spokesman Stephen McCausland said.

The sex offenders -- Joseph L. Gray, 57, of Milo, and William Elliott, 24, of Corinth -- were shot to death in their central Maine homes, officials said.

Marshall, who lived in Cape Breton, Nova Scotia, had come to Houlton, Maine, for the first time to meet his father, McCausland said.

He was driving his father's pickup, which was spotted leaving the scene in Corinth around 8:15 a.m., about five hours after the shooting in Milo was reported. The truck was later abandoned near an ice arena in Bangor, Maine.

Calling Marshall a "person of interest" in the shootings, Maine State Police alerted Boston authorities that he may be heading toward the city, McCausland said.

Police cornered Marshall on a Vermont Bus Lines coach that he had boarded in Bangor, Procopio said. Sitting 13 rows behind the driver, he pulled a .45 caliber handgun when officers boarded the bus and shot himself in the head.

When paramedics arrived, they found a second handgun in Marshall's possession, 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.