PORTLAND – A grand jury on Friday returned a murder indictment against a Scarborough man in connection with the death of Amy St. Laurent, and investigators made it clear they felt they had their man.

Jeffrey Gorman, 21, emerged within days as the prime suspect in St. Laurent’s initial disappearance in October, but it took investigators time to put together the case, said Portland Police Chief Michael Chitwood.

“He’s the only person we’re looking at. We feel confident that we have a strong case against him,” Chitwood said Friday.

St. Laurent, 25, of South Berwick, disappeared after a night out in Portland. Her body was found in early December in a shallow grave within a half-mile of a home Gorman shared with his mother in Scarborough.

“This case was a horrible, sadistic, savage murder,” Chitwood said. “When all the facts come out about the cause of her death, the community will be outraged.”

Investigators have declined to name a motive for the killing of St. Laurent or to reveal how she died. Documents containing those details have been sealed.

Four days after her body was found, police arrested Gorman after an armed standoff in Troy, Ala. He has been held at the Cumberland County Jail ever since on a probation violation.

Until Friday, investigators never named Gorman as a suspect. But a court document filed by his probation officer identified him as a prime suspect.

After St. Laurent was declared missing, hundreds of fliers with her photo and physical description were put up around southern Maine.