MISSOULA, Mont. -

The Missoula County sheriff's office says it has launched a homicide investigation into the death of a man whose body was found in the Clark Fork River in Missoula this week.

A state medical examiner determined the man had been beaten, shot and thrown into the river. He was identified as 36-year-old Gilbert George Berry, a transient from Pennsylvania who had recently arrived in the Missoula area.

Sheriff's spokeswoman Paige Pavalone says officers have identified people who have knowledge about and may have been involved in Berry's death. The sheriff's office is working with the county attorney's office to obtain arrest warrants.

A fisherman spotted the badly decomposed body on Tuesday.