Just hours before his band was to open for Soundgarden on Sunday, the bass player for Coheed and Cambria, the alternative rock band from Nyack, N.Y., was arrested on charges of robbing a pharmacy in Massachusetts to get prescription painkillers, the Associated Press reported.

The police said the bassist, Mike Todd, entered the Walgreens pharmacy in Attleboro, Mass., on Sunday afternoon and showed the pharmacists a note on his telephone claiming he had a bomb. Mr. Todd, who is 30, was said to have demanded six bottles of OxyContin and then caught a cab to the Comcast Center in Mansfield, Mass., where his band was to play the opening set before Soundgarden took the stage. He was arrested at the concert hall before the show and charged with armed robbery and possession of a controlled substance, the police said. The band played without him.

On the band’s Facebook page the other members posted a note saying Mr. Todd would be replaced by Wes Styles for the remaining dates of the tour. “We are surprised to say the least and will address the situation with Michael after the tour,” the posting said.

Formed in the mid-1990s, the band came to national attention in 2002 and has released five studio albums since then, revolving around a sci-fi story line known as The Amory Wars.