Montana woman charged in Summerset homicide

SUMMERSET, S.D. – The latest on a homicide investigation in the Pine Hills Mobile Home Park in Summerset. COURT DETAILS

Aug. 3

Law enforcement have arrested a Montana woman in connection with the death of 49-year-old Phyllis Mastin.

The Meade County Sheriff’s Office says 38-year-old Stormy Gayle Marsh of Miles City, Mont. is charged with second-degree murder.

According to an affidavit released by the sheriff’s office, Mastin was found dead by her roommate Wednesday morning at 9543 Fillmore St in Summerset. The roommate told authorities that Mastin had recently traveled to Broadus, Mont., returning with Marsh, whom Mastin had invited to stay at the house.

In an interview with law enforcement, the roommate offered her version of events leading up to the discovery of Mastin’s body. The roommate confirmed that Marsh and Mastin were the only other people in the home Tuesday night, along with her own dog. The roommate went to bed around 11:30, noting that Mastin was in her own room, getting ready for bed.

Thirty minutes later, the roommate got out of bed to turn the TV off in the living room. That’s when she noticed that everyone’s bedroom doors were closed, even though Marsh normally sleeps on the couch. The roommate heard the TV turn back on about 15 minutes after she shut it off – this time with a louder volume.

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Through a gap in her bedroom door, the roommate noticed Marsh loudly “rummaging” through items in the house. The roommate then heard a door slam and the sound of Mastin’s Mustang driving away. That’s when the roommate found Mastin dead in her bedroom.

When law enforcement arrived, Mastin was lying on her back, partially wrapped in a blanket on the bed. According to the affidavit, Mastin had several wounds on her torso and arms consistent with a sharp-edged instrument. A large knife and firearm were found under her body.

Marsh’s belongings were found scattered in the parking area outside the home.

A deputy found the Mustang near the intersection of Sturgis Road and Omaha Street in Rapid City, then saw Marsh running away, having left the driver’s side door open. Marsh was not immediately found, despite the help of a K-9 unit.

Marsh was found a short distance away, at the Rapid Motel, after law enforcement tracked Mastin’s stolen phone. Marsh was found in room 126 with Peter Bullinger. Bullinger approached police when they entered the hotel, stating that Marsh had arrived crying, with a wound on her left knuckle and what he believed to be blood in her hair.

Bullinger was allegedly told by Marsh not to contact the police, as she wondered aloud if her friend in Summerset was okay. Marsh was found in the room with a towel that appeared blood-stained. She also had several fresh cuts and scratches on her face and recent bruising on her arms and legs.

Marsh was detained for questioning, at which point she told law enforcement about Mastin fighting with her ex-boyfriend Jim that night at the home. Marsh stated that Mastin and Jim had argued – an argument that ended in a physical altercation between all three parties. Marsh claimed Jim cut her with a knife that she attempted to take away from him. She then punched him in the nose, making him bleed, while Mastin kicked him in the “nards” and face. Marsh said Mastin told her to leave.

Marsh told authorities that she left the home, waiting for Mastin at their arranged meeting spot in Black Hawk. After waiting for 20 minutes, Marsh drove to Rapid City. She claimed that she avoided police because she had a small amount of marijuana on her person and had recently smoked some.

During a search of the Mustang, law enforcement discovered a knife covered with what appeared to be blood and black hair. A shirt and pair of pants were also found, saturated in what appeared to be dried blood, according to the sheriff’s office. The outfit was wrapped in a blanket matching Mastin’s bed set.

Marsh was turned over to the Meade County jail correctional staff.


Aug. 2, 2:12 p.m.

The Meade County Sheriff’s Office confirmed the identity of the homicide victim as 49-year-old Phyllis Mastin. She was pronounced dead at the scene.

According to Sgt. Caleb Deyo, law enforcement arrived at 9543 Fillmore St. around 2:27 a.m. Tuesday for a report of a woman who was believed dead.

As the investigation continues, the sheriff’s office is being assisted by the South Dakota Division of Criminal Investigation.


11:10 a.m.

The Meade County Sheriff’s Office has confirmed that one person is in custody following the homicide.


8:44 a.m.

The Meade County Sheriff’s Office is investigating a homicide that occurred early Wednesday morning in the Pine Hills Mobile Home Park in Summerset.

Sheriff Ron Merwin confirmed to NewsCenter1 that they do have a suspect in the case, and they are currently investigating the death.

There are very few details at this point. NewsCenter1 will update the story as details become available.