JACKSONVILLE, North Carolina (CNN) -- Police believe they have found the remains of a missing Marine buried in the backyard of the prime suspect in the case and blood spatter evidence inside his home, authorities said Friday evening.



Investigators search for the body of Lance Cpl. Maria Lauterbach Friday.



Tests found the "trace of violent activity in the house" and "evidence of an attempted cleanup," said Onslow County Sheriff Ed Brown.



Investigators are treating the death of Lance Cpl. Maria Lauterbach as a murder, Brown added.



Lauterbach, 20 -- who was eight months pregnant -- was reported missing from Camp Lejeune, North Carolina, by her mother December 19.



Cpl. Cesar Armando Laurean, whom Lauterbach had accused of rape, is the suspected killer, and is being sought, Brown said.



He confirmed that Laurean had left a note, but did not divulge what it said.



Investigators told CNN, however, that Laurean left a note to his wife saying Lauterbach had committed suicide and that he buried the body.



"Evidence now is saying what he's claiming happened did not happen like he said it happened," Brown said.



Authorities searching Laurean's home found a cavity in his backyard earlier Friday.



A preliminary investigation indicated a "suspicious situation," prompting police to secure the scene and wait for daylight Saturday.  Watch authorities search for a grave »



"We think that we have found what would be the skeletal remains [of Lauterbach]," Onslow County District Attorney Dewey Hudson told reporters.



While authorities will not know for sure until Saturday, "there are certainly some strong indicators that there are human remains" buried in the cavity, he said.



"It doesn't take a rocket scientist to understand if there's a cavity out back and blood on the inside, that's probably going to be a key location for where this crime may have taken place," Brown said.



He also hinted that investigators have uncovered more twists in the case.



"I do think this case is going to be a bizarre ending, and when I say bizarre, more than just a death and a burial."



Brown stunned reporters earlier in the day by opening a press conference with the announcement: "She is dead, and she is buried."  Watch Brown describe the cavity »



Laurean, a 21-year-old from Nevada, is believed to have left the Marine base about 4 a.m. Friday, driving a black Dodge pickup with North Carolina license plate TRR1522, Brown said.



He repeatedly refused to meet with investigators, finally telling them that his attorney wouldn't let him.



The sheriff was downcast at a midday news conference.



"These cases, investigations, become personal. I just want to cry," he said. "I'm telling you, at this point, I'm down, way down."  Watch sheriff announce that Marine is dead »



Mary Lauterbach reported her daughter missing after being unable to contact her. She said she last spoke to her December 14.



In a handwritten note, the Lauterbach family in Vandalia, Ohio, mourned their loss.



"We would like to thank everyone for their prayers in this time of grieving," the note said. "Maria has been a gift for her family and friends. The outpouring of love from family, friends, neighbors and the general community has been very touching.



"Please understand that the family needs time alone to deal with this tragedy. We wish to thank everyone for their love and concern."



"They're having a very difficult time dealing with this," said Peter Steiner, a Kentucky psychiatrist who is Maria Lauterbach's uncle and Mary Lauterbach's brother. "They remained hopeful, and really, although everyone knew it was a possibility, it was very difficult when it became apparent."



Brown said a witness came forward Friday morning with a statement and evidence that convinced authorities Lauterbach was dead. Brown wouldn't name the witness, or describe Lauterbach's cause of death, except to say she died
Who left a note? Who's remains were found? Where was the trace of activity found? Who is the suspect? Who came forward?
Laurean Lance Cpl. Maria Lauterbach in the house" Cpl. Cesar Armando Laurean, a witness
question: Who left a note?, answer: Laurean | question: Who's remains were found?, answer: Lance Cpl. Maria Lauterbach | question: Where was the trace of activity found?, answer: in the house" | question: Who is the suspect?, answer: Cpl. Cesar Armando Laurean, | question: Who came forward?, answer: a witness