The investigation into the Sunday death of a 70-year-old Brinnon woman has been completed and the case is being forwarded to the Jefferson County Prosecutor's Office.

Rebecca Lynn Beck died during an argument with her roommate that escalated into a physical altercation, said Detective Sgt. Brett Anglin of the Jefferson County Sheriff's Office.

Detectives believe that Beck was angry at her 67-year-old roommate because she left a window open in the fifth-wheel trailer they shared. During an early-hours argument Sunday, Beck was pushed backward as she tried to climb into the loft area of the trailer where her roommate lived.

Bell fell backward, and injuries she sustained during her fall were fatal.

The altercation was audio-recorded, Anglin said, and backed up the roommate's version of events that Beck had been the aggressor during the dispute.

Beck was dead when authorities arrived, and was found in the lower part of the fifth-wheel.

"The deceased was found lying in that [lower] bedroom up against a dresser," Anglin said.

The death has been ruled a homicide.

The roommate, who has not been identified by authorities, was briefly detained.

She provided a full statement to law enforcement, as well as the four-minute-long recording of the altercation. She was not arrested.

The deadly argument began sometime before 1:45 a.m. Sunday, Oct. 8 when emergency responders and law enforcement were called to the 1000 block of Dosewallips Road on a report of a possibly deceased person.

An aid unit responded and the crew found Beck deceased.

Beck lived in a fifth-wheel trailer on the property west of Brinnon and shared the residence with a 67-year-old woman.

Anglin said authorities were told there had been an altercation between Beck and her roommate and Beck was pushed, which caused to her fall.

The Jefferson County Sheriff's Office launched an investigation, and Anglin said deputies learned that Beck had entered her roommate's living space and the altercation ensued.

The roommate was living in the loft of the fifth-wheel, with Beck's sleeping area in the lower part of the trailer.

Anglin said Beck "was allegedly upset over the roommate's window being open."

Beck started to climb into the roommate's sleeping area and the altercation intensified.

The roommate then pushed her back, Anglin said.

"The roommate advised that after [Beck] had fallen, she was unresponsive," Anglin said.

An autopsy was completed Oct. 11 and it found "a partial transection of the brain stem, along with atlanto-occipital dislocation, a blocked force craniocervical injury and ground level fall," Anglin said.

No other injuries were found.

Parts of the case were forwarded to the prosecutor's office on Oct. 10, and additional information followed.

The roommate was the only witness to the incident.

"The evidence at this point suggests that it was a single event, which was audio-recorded at the time and consistent with the deceased being the aggressor," Anglin said.

Beck's next of kin has been notified, Anglin said, and they have been allowed to listen to the audio recording.