Docs: Burien man may have stabbed girlfriend, roommate to death over breakup
Sep 16, 2025, 5:45 AM
Burien Police arrive at a crime scene late at night. (Photo courtesy of KIRO 7)
(Photo courtesy of KIRO 7)
A man has been charged with two counts of first-degree murder for what prosecutors call the “horrific” deadly stabbing of his girlfriend and her roommate.
Late night on Sept. 8, law enforcement responded to a call for a man who was down and bloodied on the grass outside the Montrose apartments on S 152nd Street in Burien.
That man was identified as 29-year-old Marvin Ortiz Montecinos.
First responders treated Montecinos at the scene and took him to the hospital. He had multiple injuries on his neck, chest, and back.
Deputies followed a blood trail from the man outside to an apartment on the third floor.
The door to the apartment was wide open, so law enforcement went inside, calling out to anyone who might be inside.
They got no response.
Going through the home, they found that all the drawers and cabinets in the kitchen were open as if they had been searched before deputies arrived. No other rooms had shown signs of being rifled through, court documents detailed.
Deputies continued through the home, where they found two women covered in blood, dead in a bedroom.
One of the women was found nude with a towel over her legs. Court documents said she was stabbed over 40 times, and that she may have been taking a shower when she was attacked.
The other was found with around 20 stab wounds.
From the hospital, Montecinos told detectives that he was sleeping in the apartment and was awoken by screaming. He said by the time he had gotten up to see what was wrong, both women had been stabbed. He said a person was hiding inside the apartment and then stabbed him before running out, court documents detailed.
However, according to court documents, detectives said his timeline of events didn’t match up with cell phone records that showed messages between Montecinos and one of the deceased women. These messages were sent between both people when Montecinos had alleged that the woman was already dead.
Blood forensics at the scene did not match up with what Montecinos said happened, according to court documents.
Detectives noted that there was only one set of footprints that led from the bedroom to the front door, and they matched with the sandal that Montecinos was wearing when 911 arrived, court docs said. There was also no sign of forced entry, court documents said.
Nurses at Harborview Medical Center said that Montecinos’ wounds were superficial, unlike the numerous deep stab wounds suffered by both women.
The women’s injuries were so extensive that it appeared “the defendant was attempting to slice and saw his victims, and not simply stab them,” court documents said.
Detectives believe that the “horrific” stabbings may have been prompted by one of the victims breaking up with Montecinos. Court documents say he may have brought this up just an hour before they were stabbed.
Detectives also believe that the woman’s roommate was killed for trying to intervene, court documents said. It’s believed she was in the shower or getting ready to shower when she heard her friend scream.
Montecinos has been charged with two counts of first-degree murder.
Bail has been set at $10 million, since prosecutors believe he is a flight risk.
His next court date is scheduled for Sept. 17.
