Police on Tuesday identified the woman as 21-year-old Britney Cross of Edgerton. Janesville Police Chief David Moore says Cross dried of a blunt-force head injury.
The Wisconsin State Journal reports Cross' 28-year-old boyfriend is the only suspect in her death.
The man was arrested Sunday night after allegedly stabbing his 28-year-old roommate and threatening the roommate's pregnant girlfriend.
Investigators say before the stabbing the suspect said he had killed three people that night and "we are all going to die."
Police say the suspect had said he was going to drink and do drugs with a woman under a bridge. Cross' body was found south of the bridge.