A convicted murderer assigned to an inmate work crew at a downtown state government building escaped by walking away through a crowd of people, authorities said.

Timothy Barry, 38, who had served 10 years of a life sentence for the kidnapping and killing of his sister-in-law, was last seen around 9:15 a.m. Tuesday on the 22nd floor of the Saltonstall Building on Cambridge Street, state officials said.Barry was convicted of second-degree murder after he confessed to killing Nancy Ellen Brown, 23, who died of a skull fracture after being hit with a blunt instrument in 1977.

He told police he kidnapped the victim from her parents' home in Everett, blindfolded her and drove her in her car to Crane Beach Reservation in Ispwich, where she was found buried in sand dunes.

"There is no indication that Barry is dangerous, but anyone on escape should be considered dangerous," state Correction Department spokeswoman Kathy Ayres said.

Barry, who was incarcerated at the Bay State Correctional Center in Norfolk, was part of a work crew assigned to move furniture and clean windows and floors in the Correction Department's former parole office, Ayres said.

He apparently was able to escape by mixing in with crowds of people entering the building in the morning, she said. Barry is eligible for parole in 1994.