A source told PEOPLE that Brooke Mueller's twin sons "are fine and with their nanny"

Shortly before Brooke Mueller and her twin sons were reported missing in Utah on Wednesday, the ex-wife of Charlie Sheen seemed content and was “casually dating,” a source tells PEOPLE.

On Tuesday night, Mueller, 39, walked into a Salt Lake City bar barefoot, with her kids — Bob and Max, 7 — and the family nanny, TMZ reported. While in the bar, Mueller and the nanny got into an altercation, causing someone to call the police. Early Wednesday morning, the Salt Lake City Police Department attempted to locate Mueller before a source told PEOPLE that “the boys are fine and with their nanny” after “Brooke went off of her medications.”

But prior to the incident, the mother of two, who wed Sheen in 2008 and filed separate divorce petitions in 2010, started seeing skin care creator Peter Thomas Roth, the source says.

“He met Brooke in L.A. They had lunch. He went to the Hearst Castle Benefit with her, which was the last time he saw her. The last time he spoke to her was around 11 yesterday morning,” the source tells PEOPLE. “They were dating, not exclusively. He was newly single after almost 20 years [with wife Noreen]. It’s like anyone who is going through divorce — you just kind of go out.”

According to the source, skin care line founder Roth, who is friends with Mueller’s parents, met her this past summer in Los Angeles.

“It has not been that long. They were casually dating. They’d gone to a few things together … It was not super serious, at all. He went out with her a handful of times,” the source says, adding that if the pair — who don’t live in the same city — called it quits, “I don’t think this was at the point where anyone would be getting dumped. It wasn’t that serious.”

In response to the situation, Sheen told TMZ, “I’m just trying to get my kids home safe. I have no other details that relate to the ongoing event.”

Earlier this year, a source told PEOPLE that Mueller had checked herself into rehab, and it was not the first time that Mueller had sought help — in December 2011, she entered herself into a “long-term, in-patient treatment center” following an arrest for alleged cocaine possession and assault.

Though Sheen, 51, issued a brief comment on Tuesday’s incident (he is “just trying to get [his] kids home safe”), Mueller has yet to address the reports as of publication time.