"Kristin is totally freaked out and hoping for the best" a source close to the family tells PEOPLE

By Dan Wakeford
Updated December 07, 2015 07:15 PM
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Credit: Courtesy Grand County, Utah, Sheriff's Office

Kristin Cavallari has stood by her brother Michael through thick and thin.

As Utah police search for Michael, whose car was discovered abandoned on a highway in the state the day after Thanksgiving, a source close to the family says the missing man has had a difficult past.

“Her brother was always a troubled kid and there was always drama with him,” the source tells PEOPLE.

Just says before his disappearance, Michael was arrested on Nov. 23 and briefly held in an Orange County jail, according to Orange County Sheriff’s Department records. He was arrested with a loaded shotgun outside the city hall in Dana Point, California , NBC Chicago, Fox News and Entertainment Tonight report. According to police documents obtained by the news outlets, an unnamed woman also claimed Cavallari was outside her home carrying a shotgun. She also said the pair had gotten into an argument before the incident. His 2014 Honda Civic was found abandoned off a Utah highway on Nov. 27.

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“He gave his parents a hard time. He’s completely opposite to Kristin who is levelheaded and business orientated,” says the source.

But Michael and Kristen have always been close, the source adds.

“She was always very protective of him,” the source says. “She was always trying to help him. He had been trying to produce reality shows awhile ago, but it didn’t work out.”

On Monday, Kristen, 28, posted an emotional thank you to fans for the support following the disappearance, saying she remains “hopeful.” She also shared a photo of the siblings enjoying a day on the beach as children.

The source says the Cavallari family has banded together since the disappearance.

“They are all – apart from Kristin’s dad [Dennis], who is in California – holed up in Chicago giving each other emotional support. They don’t have any idea what has happened to him and Kristin is totally freaked out and hoping for the best.”

Anyone with information regarding Michael should contact the Grand County Sheriff’s Office at 435-359-8115.