Friends of musician Carter Albrecht believe the combination of alcohol and the stop-smoking drug Chantix may have caused the bizarre behavior that led to his death on Sept. 5.

ABC News reported Sept. 19 that Albrecht, 34, the keyboard player from the band Edie Brickell and the New Bohemians, was shot to death in Dallas after pounding on the door of his girlfriend's neighbor's house in the middle of the night. Albrecht and his girlfriend, Ryann Rathbone, had recently started taking Chantix as part of a pledge to stop smoking.

However, Rathbone said that the couple began having vivid and frightening dreams soon after they began taking the drug -- "nightmare kind of, hallucination kind of dreams where you don't know if it's real or not," she said. Drug-maker Pfizer warns that changes in dreams can be a side-effect of taking Chantix.

On the night he was killed, Albrecht began hallucinating after drinking, verbally and physically attacking Rathbone. He then left her house and began banging on the neighbor's door. The neighbor fired what he termed "a warning shot" through the door, killing Albrecht.

Anecdotal evidence points to a variety of problems experienced by some of the 3 million Americans taking Chantix, including contemplation of suicide and bouts of depression, sometimes triggered by alcohol use. Ponni Subbiah, a spokesperson for Pfizer, said, "To date there is no evidence to suggest that Chantix is associated with violent behavior. And I think it's important to keep in perspective that alcohol use in itself is associated with violent behavior."