Nicole Marie Ryan was arrested at the scene on the 400 block of North Meldrum Street in Old Town Fort Collins. Her fiance, whose identity hasn't yet been released, was transported by Poudre Valley EMS and was declared dead about the time he arrived at the hospital, said Fort Collins police Sgt. Kristy Volesky.

Ryan called 911 at about 11:25 p.m. Friday and told dispatchers that she'd injured her husband. The incident occurred in the basement bedroom of a home they shared with Ryan's mother, brother and another roommate, Volesky said.

No other people are believed to have been home during the incident, and details of the argument are unclear. Ryan's booking charges include a domestic violence enhancement to second-degree murder.

The crime scene was being processed Saturday as the blue house with yellow trim was surrounded by yellow police tape. A woman who exited the house with a bag of pet food declined comment.

The Larimer County Coroner's office conducted an autopsy of the victim Saturday but was having difficulty finding next-of-kin, as the man had had a transient lifestyle. The man's name is to be released once his family has been notified.

The case remains under investigation, and anyone with information is asked to call Fort Collins police Det. Keith Maynard at (970) 221-6540.

This is the second murder case Fort Collins police have investigated this year.

Ryan's criminal history includes a 2008 theft case out of Fort Collins involving allegations of providing false statements for prescribed drugs, and theft under $500. That case was settled with a plea deal of guilty to possessing a gram or less of a schedule II controlled substance. She was given a two-year deferred sentence.

In Greeley last year, she was accused of motor-vehicle theft. She pleaded guilty in Janurary 2012 and was sentenced to 60 days in jail with two years of probation.