Police said her disappearance is now being investigated as a homicide, and that Ramos' former roommate, 54-year-old Kwang Chol "KC" Joy, has been arrested in her murder. He has been booked into Orange County Jail and is being held on $1 million bail.
Detectives searched the apartment the two shared Friday night and removed 11 bags of evidence, and Ramos' dog. Ramos had lived with Joy for the last year and a half. Joy said they were very close, and even went on a cruise together.
Joy told Eyewitness News shortly after Ramos disappeared that he had been questioned numerous times by police. He said he provided a DNA sample, and even allowed police to photograph his nude body.
When Eyewitness News asked Joy if he had anything to do with Ramos' disappearance, he denied any involvement.
"Not at all. Not at all. I just need her back. I need her to come back because she's my best friend, actually she's my only friend, my only family member I have, so I miss her," he said.
Ramos, 36, was an Army sergeant, Iraq War veteran and California State University, Fullerton student. She was last seen May 2 on surveillance footage outside her apartment in Orange. Police say she was alone.
Authorities are not saying how Ramos was killed, and the motive is still unknown.
Her body was discovered Thursday after residents reported a terrible odor in the area. Responding authorities found the body in the brush near the intersection of Santiago Canyon and Jackson Ranch Road.
The body was removed Thursday night, but a white tarp remained on scene. Authorities say there is important evidence under the tarp, which was seen weighted down by rocks Friday morning. An autopsy completed Friday confirmed the body was that of Ramos.
Earlier in the day, a cadaver dog was scouring the hillsides near Modjeska Canyon looking for potential evidence.
Modjeska Canyon is located in unincorporated Orange County, but police from the city of Orange came to the scene as part of their investigation.
Her sister said Ramos was looking forward to graduating from CSUF this month with a degree in criminal justice.
Ramos was remembered in a statement released by CSUF President Mildred Garcia, which said the campus community was "profoundly sad" to hear of Ramos' death.
"Maribel was a beloved student and military veteran, who was actively engaged here on our campus and in the community," the statement read, in part. "She was a wonderful role model for our students, faculty and staff. And we honor her for her past service to our country as an airborne paratrooper in the Army and her commitment to her education. We continue to offer our support to her family and friends during this exceedingly difficult time."
