FORT COLLINS, Colo. -- A University of Northern Colorado sophomore who was reported missing last weekend is now believed to be dead and police say they have the suspect who allegedly committed the murder.

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Lacy Miller's Family & Friends React To The News

Jason Clausen, 22, was arrested Tuesday night on suspicion of first-degree murder and first-degree kidnapping, but his arrest wasn't announced until Wednesday.

Police had not found the body of Lacy Miller, 20, as of Wednesday afternoon, but said they recovered personal belongings, including her identification.

Investigators received a tip from a person which led them to Clausen. The person's affidavit was sealed because the investigation is still active, so 7NEWS does not have the details concerning her kidnap and murder.

According to records from the Colorado Bureau of Investigation, Clausen was arrested Jan. 13 -- just five days before Miller went missing -- for trespassing, theft and tampering with a car with intent to steal.

In 2000, he was charged with racing his car and careless driving.

But before his brush with the law, Clausen was a youth volunteer with the Fort Collins Police Explorer Scout program in 1998, 7NEWS reported.

Clausen, who is unemployed, was supposed to leave for the military Wednesday, police said.

Miller's friends and family, who spent days asking for help to locate the missing co-ed are now dealing with their loss.

"I don't know how you do a life without Lacy. She was a bright light and the world is a dimmer place," said Wendy Cohen, mother of Miller.

"She was a very enthusiastic, happy person. She was a good solid student, very focused. She was just right on track, zooming along here doing very well. She knew what she needed to do," said Mary Borg, Miller's university advisor.

Miller was last seen around 1:30 a.m. Saturday, when she dropped off a girlfriend in Fort Collins and said that she was tired and heading directly home.

Her parents reported her missing after finding her car near their home, where she lives. Miller also missed work Saturday and a movie date with friends.

Miller's family and friends said that this was uncharacteristic of her because she is a very responsible and conscientious woman.

Miller's car, a 2002 black Mitsubishi Mirage, was found locked and parked on the street two doors away from her parents' home. Family members said that this was odd because she only parked on the driveway or in the garage.

Police had said earlier in the week that her belongings had been removed from the car, but there were no signs of foul play. A bloodhound failed to find any trail from the car, which could indicate that she got into another car after stepping out of hers, 7NEWS reported.

Police officers, Miller's family and friends, and community members had been actively looking for clues about her whereabouts. They searched the hillside near her home and posted fliers about her around the school in Greeley and in Fort Collins.

A $10,000 reward was offered for more information about her disappearance.

Fort Collins police for days said that there was no evidence of foul play and that the investigation was being handled as a missing person's case.

Investigators watching her cell phone and credit cards said that there have been no activity on them since she disappeared.

Miller was studying to be an elementary school teacher.