A Portage man is now a person of interest in a missing persons case they say could be a possible homicide investigation.

Theresa Lockhart has been missing since May 18. On Friday, police named her husband Christopher Lockhart, a person of interest, citing his lack of cooperation in the case.

"They were hitting a really rough patch," Jen Zimmerman, Theresa's friend said.

Zimmerman has known Theresa Lockhart and her husband Chris for years. She and Theresa went to college together and stayed close friends. She says she last spoke to Lockhart, a teacher for Schoolcraft High School, the day before she went missing.

"She was talking about her school contract and talking about looking at new job possibilities," Zimmerman said.

Lockhart was last seen around 10:00 pm on May 18, leaving her home. Police later found the 44-year-old's car at a Park and Ride a few miles away.

Authorities named Theresa's husband, Christopher Lockhart, a person of interest in her disappearance, calling the case a possible homicide investigation.

Zimmerman spoke to Chris on the phone last week.

"He was beside himself when I talked to him he was broken down in tears," .

WZZM 13 asked Zimmerman if she was surprised to hear Chris was a person of interest.

"Chris has been struggling with grief with his mom's death and that's been on-going so yes and no," she said. "Because of his behaviors that grief process has brought about."

Zimmerman would not elaborate on those behaviors but says Chris had made a few poor decisions.

"He's made some choices that have been really hard for her [Theresa] to have to work over, the last several months. He finally started to get the help he needed but like anything, it's a step forward a step back."

Despite Portage police's belief that this may not be a positive ending, Zimmerman is hopeful.

"I don't want to think about foul play, I don't want to think about bad ends, frankly that scares me," she said.

Jen did confirm to WZZM 13 there was a domestic violence case between the two earlier this year, but it was dropped.

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