PORTLAND – A man who walked up to the homes of two convicted sex offenders and shot them to death Easter morning had a digital image on his computer of Jesus armed with an assault rifle while knocking on someone’s door.

Stephen Marshall, who had embraced Christianity a short time before the killings, once called pedophiles the “scums of the earth.”

But more than 500 pages of Maine State Police investigatory materials obtained by The Associated Press under the Maine Freedom of Access Act provide no clear answer as to what drove the 20-year-old from North Sydney, Nova Scotia, to kill.

“Sometimes there’s no completely rational answer for a completely irrational act,” said Stephen McCausland of the Maine Department of Public Safety.

Marshall looked up at least 34 names on Maine’s online sex offender registry before targeting two of them, Joseph Gray, 57, of Milo and William Elliott, 24, of Corinth, while visiting his father in Maine.

After abandoning his father’s truck in Bangor, Marshall took a bus to Boston, where he killed himself on the bus outside South Station after being tracked down by police.

The killings renewed the debate over the safety and fairness of posting the names of convicted sex offenders online. In addition to checking out Maine’s registry, Marshall looked at a national one and those in New Hampshire and Vermont, authorities have said.

The documents obtained by the AP help to round out a picture that emerged in news reports last April depicting Marshall as a skinny young man who had been picked on at school and who shared his father’s interest in guns. In fact, the bullying was severe enough that Stephen Marshall once was hospitalized, his father said.

Days before the killings, the first thing Marshall wanted to do when visiting his father in Houlton was to go to a gun range, something he couldn’t do in Canada because his mother and stepfather didn’t keep guns, the documents show.

Bad weather prevented target practice, but Marshall spent the two nights before the killings cleaning his father’s guns, his father told investigators.

Though he was described as quiet and reserved, Marshall lashed out at least once, threatening to kill his stepfather when he criticized Marshall for losing a job at a call center, his mother told investigators.

An analysis of Marshall’s computer showed he had visited at least one Web site that contained information on how to plan and execute a murder, according to a report by Scot Bradeen of the Maine Computer Crimes Task Force.

The killings shocked friends, family and acquaintances of Marshall, who was described universally as kind and quiet.

Marshall was born in Texas and lived in Idaho and Arizona in addition to Canada. Sometimes he lived with his father, sometimes with his mother. He moved to Cape Breton, Nova Scotia, to live with his mother and stepfather in 2003.

He moved out after the argument in which he threatened his stepfather, and he lived for a short period in a boardinghouse. He left after a fellow tenant propositioned him for sex, and he later told his father that a pedophile lived at the boardinghouse, the documents indicate.

“Stephen was upset that the man made a pass but was even more upset that he was living next door and didn’t know he was a pedophile,” his father told police.

Though he apparently didn’t dwell on the incident, he was protective of his younger sister and once told his mother that pedophiles were the “lowlifes” and “scums of the earth.”

The remark didn’t alarm his mother, Margaret Miles, who told police she felt Marshall was getting his life together and had become a Christian in January. Marshall gave up smoking, took up jogging and began thinking about the future, Miles told investigators.

His father, Ralph Marshall, reported that his son was planning to move to Maine and that they had driven around looking at homes just days before the killings. His father also noted that he’d become a Christian, though he said it was just a week before the killings.

But there was a darker side, as well.

His laptop had folders with information downloaded from sex offender registries, the documents show. Belongings he left at his father’s house included a camouflage backpack with survival gear and three books, “Art of War,” “SAS Survival Guide” and a Bible. Stephen Marshall had tried to join the Army, but was rejected because of asthma, officials have said.

Though Margaret Miles believed her son was getting his life together, she worried about him because he seemed to have trouble concentrating. She reported that he fainted once and that she had noticed him trembling.

Neither Miles nor Ralph Marshall could be reached Thursday for comment. Miles also invoked documents under the Freedom of Access Act.

On the night before Easter, as his father slept, Marshall took a Colt AR-15 rifle and two handguns from his father’s safe, slipped out a bedroom window and drove off in his father’s pickup, the documents indicated.

Among the lingering mysteries is why Marshall chose his two particular victims.

Gray’s name was on a state Web site because he had moved to Maine after being convicted in Massachusetts of sexually assaulting a child under 14. Elliott was convicted of having sex with his girlfriend, who was underage at the time, officials said.

A global positioning device on the computer enabled investigators to reconstruct Marshall’s movements from the time he stole the truck until he abandoned it. But there was nothing on Marshall’s computer to suggest why he zeroed in on Elliott or Gray instead of other offenders, Bradeen said. The GPS indicates he went to the homes of two other sex offenders, but neither was harmed, Bradeen said Thursday.

There has been speculation that Marshall was once a victim of a pedophile. If he was, he didn’t tell anyone interviewed by the police, and there’s no mention of that on his computer, the documents indicate.

“We were looking for something that would establish his state of mind, why he would do this. I found absolutely nothing,” Bradeen said.