Corinth, Maine ? A man who shot two sex offenders to death in Maine got their names from the state’s online sex offender registry, authorities said Monday, renewing fears that such lists expose ex-convicts to vigilante violence.

The gunman, Stephen A. Marshall, a 20-year-old from Canada, committed suicide Sunday night in Boston after being cornered aboard a bus by police.

Investigators were uncertain what relationship, if any, Marshall had with the two victims, who were killed Easter Sunday morning at their homes 25 miles apart.

But the two men were among 34 names Marshall had looked up on the state Web site, said Stephen McCausland of the Maine Department of Public Safety. Investigators said they discovered he visited the Web site because he typed in his name to receive extra information online, including street addresses.

The Web site was disabled while police searched for Marshall but was restored Monday afternoon.

“The Web site is back on. It is there by law. The reason why the information is available to the public is well-documented,” McCausland said. The sex offender registry is designed to let people know of child molesters and other sex offenders in their midst.

All states have sex offender registries, and almost all of them post the information online.

But the killings added to a growing unease with such Web sites. Jack King from the National Association of Criminal Defense Lawyers in Washington said making public sex offenders’ addresses can be an invitation to violence.

Harassment, vandalism, assaults and even killings of sex offenders have been reported from coast to coast.

Maine State Trooper Dave Yankowsky, left, and detective Jay Pelletier search the driveway of slain sex offender Joseph L. Gray, 57, in Milo, Maine on Monday, April 17, 2006. Gray and another sex offender, William Elliott, 24, of Corinth, were found shot to death in separate incidents on Sunday.

“There are going to be crazy people out there,” King said. “And there’s going to be vigilantism.”

After New Jersey passed a public disclosure law on sex offenders in the 1990s, the brother of an offender was nearly beaten to death with a baseball bat when he was mistaken for his brother, King said.

In New Hampshire, Lawrence Trant went to prison after pleading guilty to the attempted murder of two convicted sex offenders whose names and addresses he found on an Internet registry posted by the state.

A sex offender Web site in Washington state was cited in the slayings of two convicted child rapists last summer. Michael Anthony Mullen, 35, pleaded guilty to murder and was sentenced to more than 44 years in prison.

In Maine, the registered sex offenders shot to death were Joseph Gray, 57, of Milo, and William Elliott, 24, of Corinth.

Gray’s name was posted on a state Web site because he had moved to Maine after a Massachusetts conviction for sexual assault on a child under 14, McCausland said. Elliott was convicted of having sex with an underage girl, he said.

When he shot himself, Marshall had with him a laptop computer along with two handguns, said Dave Procopio, spokesman for the Suffolk County, Mass., District Attorney’s Office.

Marshall, a 20-year-old restaurant dishwasher from North Sydney, Nova Scotia, had come to Houlton, Maine, to visit his father, authorities said.

Investigators believe he used his father’s pickup during the killings. The father had not realized his son and truck were missing, McCausland said. Marshall also took two handguns and a rifle from his father, the spokesman said.

Police tracked Marshall to Boston after finding his pickup abandoned in Bangor and then discovering bullets of the same caliber used in the killings in a bus stop rest room.