CAPE BRETON ISLAND, Nova Scotia – Family members, co-workers and American and Canadian police don’t know what drove a 20-year-old dishwasher at a North Sydney Chinese restaurant to apparently murder two convicted sex offenders in Maine before fatally shooting himself Sunday night on a crowded, Boston-bound bus.

The family of Stephen A. Marshall said Monday they didn’t even know he had left town.

“We were sitting down yesterday about to eat Easter dinner and we found out about this at that time,” said his stepfather, Keith Miles of Bras D’Or. “As a family we had no idea that Stephen was even in the States. We thought he was in North Sydney.

“We’re devastated by this and as confused about it as everybody else is.”

Marshall was pronounced dead at 11:24 p.m. Sunday at Boston Medical Center from a massive head wound. Maine police investigating Sunday’s shooting deaths of Joseph L. Gray, 57, of Milo, Maine, and William Elliott, 24, of Corinth, Maine, received a tip that their prime suspect, Marshall, was on the bus and contacted Massachusetts police, who stopped it outside Boston’s South Station bus terminal around 7:25 p.m.

That’s when Marshall discharged a .45-caliber handgun he had taken earlier from his father, Ralph Marshall, in Houlton, Maine.

No one else was injured on the bus, but five passengers reportedly were splattered with blood.

Miles said he couldn’t understand what happened.

“All that we can say about Stephen is that he’s always been pretty much a model citizen,” he said. “He doesn’t have as much as a traffic ticket. We don’t know where all this came from. It’s a mystery to us at this point.”

Charlie McArthur, 39, assistant manager of the Canton Restaurant on Commercial Street in North Sydney, said Marshall washed dishes there for about a year and was an ideal employee.

“He was very polite, a good kid, quiet – never any problems with him.”

However, after a three-day break in his schedule starting Wednesday, he oddly failed to show up for work Saturday. Restaurant staff tried to contact Marshall, but failed. Someone reached Marshall’s mother in Little Bras D’Or, who said he was in Maine visiting his father and was having car trouble.

McArthur said Stephen Marshall had dual citizenship and listed Phoenix, Ariz., as a former home on his application. The young man made minimum wage and was renting an apartment on Regent Street with others his age.

He never heard of Marshall badmouthing sex offenders, or anyone else.

“He never said anything bad about anybody,” McArthur said.

He said the killings were a major shock.

“It’s baffling to see somebody that you work with on CNN,” the assistant manager said. “At first you don’t believe it, then as the pieces fall in together you’re like everybody else – you try to find out why and what happened.”

The restaurant didn’t open Monday because of the situation, and plans for today hadn’t been set, he said.

Ralph Marshall moved into an apartment on Court Street in Houlton one or two years ago, according to Jerry York, who lives across the street.

York knew Ralph Marshall enough to say hello, but they didn’t talk much, and the new neighbor never mentioned his son.

“He was a friendly guy and kind of kept to his own from what I could see,” York said.

Neighbors said Marshall lived alone and, when he arrived, had Colorado license plates on his truck when he moved to town.

A taped message at the Houlton Band of Maliseet Indians states that Ralph Marshall is employed there as an economic developer. Houlton is located close to the Canadian border, near Woodstock, New Brunswick.

Investigators interviewed Ralph Marshall at his home Sunday.

“We have talked to him, and I suspect we will be talking to him again,” McCausland said.

The principals at Riverview High School in Coxheath and Memorial Senior High School in North Sydney said they hadn’t heard of Stephen Marshall.

Staff Sgt. Russell Ivey of Cape Breton Regional Police also had never heard of Stephen Marshall before all this happened.

“The young fellow’s never been in any trouble with the police here. Not even a parking ticket.”

He said police think Stephen Marshall grew up in Little Bras D’Or, then spent some time living with his father in the United States before returning to Cape Breton.