Frazee, 32, was arrested on suspicion of first-degree murder and suspicion of solicitation of first-degree murder for the death of his fiancée, Woodland Park Police Chief Miles De Young said on Friday.
A lawyer from the public defender's office was appointed to represent Frazee, according to court documents. "We just watched her - she matured through the years, turned into a handsome young lady".
Berreth's phone was tracked to a location near Gooding, Idaho. De Young said that only one person was arrested, but noted that additional arrests were a possibility, KOAA News reported.
Berreth's aunt, Renee Stanfill-Marasco, apparently posted on Facebook that her niece had broken off her engagement to Frazee the day she was last seen alive.
Berreth has not been seen since Thanksgiving when she was seen at a Woodland Park Safeway store with her daughter.
Berreth's cousin, Jodi Garretson, told Inside Edition's Senior Correspondent Les Trent that her parents were "absolutely devastated" by the development in the investigation.
Frazee was transported to the Teller County Jail following his arrest, the law enforcement source said.
Berreth's body had not been found as of 10 a.m. Friday, said Woodland Park Police Chief Miles De Young. The couple's 1-year-old daughter is now in protective custody.
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Frazee was the last person to see Berreth alive, investigators said.
Cheryl Berreth told NBC News that her daughter's relationship with Frazee had been good and loving.
Last week, investigators searched Frazee's 35-acre property, located in a small town south of Denver called Florissant but turned up no trace of Berreth.
It's unclear what charges Frazee faces.
Investigators with the Colorado Bureau of Investigation, the Woodland Park Police Department and the FBI were spotted Thursday evening carrying large brown bags out of Berreth's home, and a firefighter was seen carrying a ladder into the house, CNN affiliate KMGH reported.
Berreth's mother told CBS News' Nikki Battiste last week the couple was excited to get married, but hadn't set a wedding date.
Kelsey Berreth was "a little reserved and sometimes soft-spoken" but often talked about Frazee, whom she was dating when she was a flight instructor at Springs Aviation in 2016, company owner Bobby Hosmer said.
Frazee was being held without bond. The search and arrest affidavits will stay sealed during the investigation, he said.
Frazee is being held without bond pending his next court appearance, set for December 31, KMGH reported.