AUGUSTA – A convicted arsonist whose getaway from a bank robbery in September was foiled by an off-duty sheriff will spend 10 years in prison.

Jonathan C. Linton, 36, of Augusta, who spent 15 years in prison for setting a 1994 fire that destroyed Litchfield Central School, pleaded guilty Tuesday in Kennebec County Superior Court to robbery and theft.

“I was just trying to pay the rent,” Linton told Justice Nancy Mills. Linton also said he was sorry for the robbery.

Linton was on probation when he entered the Savings Bank of Maine in Manchester on Sept. 13, brandished a handgun and demanded money. He made off with about $5,000, Assistant District Attorney Paul Rucha said.

The cash was still in the black lunch sack that Linton had given the bank teller when sheriff’s deputies stopped his vehicle. Linton told them he had used a pellet gun and offered to show them where he had tossed it, Rucha said.

Authorities were alerted by Peter Mars, an off-duty Franklin County sheriff’s deputy, who saw the robbery through the bank’s drive-through window and followed the suspect’s vehicle.

Mars later told a reporter, “I see this guy in a ski mask jumping back and forth and waving what appeared to be a semi-automatic handgun,” Mars said. “I could tell he was ordering them to give him all the money. I thought, ‘Is this a movie or what?’“

Linton’s attorney, Pamela Ames, said Tuesday that Linton needed rent money so he, his wife and their newborn could keep their apartment.

Linton was released from prison Aug. 21, 2009. He was 20 years old when he pleaded guilty to the arson at the school and was sentenced to 25 years, with all but 17 years suspended, and eight years’ probation. He served 15 years.

On Tuesday, Mills ordered Linton to serve the remaining eight years of the arson sentence, then added a consecutive term of 10 years in prison, with all but two years suspended and three years’ probation.