Police arrest boyfriend in missing Phoenix woman case

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Mustafa's body still hasn't been found. (Source: 3TV/CBS 5) Mustafa's body still hasn't been found. (Source: 3TV/CBS 5)
Robert John Interval Jr., 37 (Source: Maricopa County Sheriff's Office) Robert John Interval Jr., 37 (Source: Maricopa County Sheriff's Office)
Phoenix mom Christine Mustafa has been missing since May 10. (Source: 3TV/CBS 5) Phoenix mom Christine Mustafa has been missing since May 10. (Source: 3TV/CBS 5)
Mustafa also disappeared without her 8-month-old baby, who was staying with a caregiver. (Source: 3TV/CBS 5) Mustafa also disappeared without her 8-month-old baby, who was staying with a caregiver. (Source: 3TV/CBS 5)
PHOENIX (3TV/CBS 5) -

Police have arrested the live-in boyfriend of a missing north Phoenix woman in connection to her disappearance.

Robert John Interval Jr., 37, was arrested and booked on one count of first-degree murder.

The body of Christine Mustafa still has not been found, Sgt. Jonathan Howard with the Phoenix Police Department said.

[RAW VIDEO: Spokeswoman for missing north Phoenix woman's family speaks about arrest (Part 1)]

[RAW VIDEO: Missing woman's family spokeswoman speaks about arrest (Part 2)]

The 34-year-old was last seen by a coworker on May 10. A few hours later she spoke to her sister by phone. On May 11, she didn't show up for work and her family called the police.

[ORIGINAL STORY: Phoenix police ask for help finding missing Phoenix mother]

When police went to her home, there was no answer. Police said Interval arrived at the home and told them Mustafa had left for work and was walking there.

On May 16, police searched the house and reportedly found her wallet, cellphone and car. They also reportedly discovered bedding that appeared to have small amounts of blood on it.

Investigators also took Interval's handgun and cellphone, documents said.

A search warrant says the boyfriend explained to investigators that the couple “got into a verbal argument on the night of May 10 over his beliefs that she was cheating on him.”

The documents describe a conversation one of Mustafa’s coworkers had with investigators telling them the boyfriend had even threatened to kill Mustafa.

Mustafa also disappeared without her 8-month-old baby, which concerned family members.

While police have made an arrest, they're still looking for more information. If you have any, call Phoenix Police or call Silent Witness at either 480-WITNESS (948-6377) or 1-800-343-TIPS (8477). Spanish speakers may call 480-TESTIGO (837-8446). (Click or tap phone number to call from this story on your mobile device.)

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