Eric Stewart, 51, allegedly murdered his wife, Denise Bohn-Stewart, 45, in their Royalton Township home, Lt. Charles Christensen tells PEOPLE.
Christensen says the couple's three young children – ages 10, 9 and 8 – were home and that one of them called 911 after hearing gunshots.
"They heard something; they didn't see anything," Christensen says. The children were unharmed and were taken to a safe location.
Christensen says Denise had multiple gunshot wounds, and that when police arrived, Denise and Eric were in two separate rooms.
He says investigators had learned "they were having some marital issues. They had been for some time."
Gayle Olson, Board Chairman and President of 98.3 The Coast, the radio station in St. Joseph, Michigan, for which Denise co-hosted the morning show, tells PEOPLE, "She recently made it clear that she was moving on and that a divorce was likely, although nothing had been formally filed."
He says that Eric worked as a maintenance supervisor at the Cook Nuclear Plant, one of the largest employers in the region.
Beloved Personality and Fierce Advocate for Breast Cancer Research: 'A Force of Nature'Denise was the co-host of Denise and Johnny in the Morning, the morning show on 98.3 FM, and also did news reporting for the station.
On air, says Olson, "She was very outgoing, very friendly, and very much about the audience and listeners and not about her. So many morning shows are star-centric. But she was about the community and the causes."
Olson says Denise began her career at the station about 25 years ago and returned a little over a year ago so she could have greater schedule flexibility to spend time with her children and devote herself to her work fighting breast cancer. In addition to her work on the radio, she was the development director of the Susan G. Komen Foundation's Michigan affiliate.
She had survived breast cancer herself after being stricken when her youngest child was just two months old. She had also survived a serious car accident in the 1990s that disabled her for months and required her to get metal rods inserted into her neck.
"This is someone who fought back from two life-threatening situations and was absolutely at the top of her game," Olson says, adding that she became "kind of a role model for the young, active, mom demographic. Everyone looked up to her."
Jennifer Jurgens, Executive Director of the Susan G. Komen Foundation's Michigan affiliate, tells PEOPLE that Denise was "a tireless advocate for breast cancer research and for helping people locally find it early and pay for [treatment]. Being a survivor herself, she could have empathy, she could relate."
As development director, Jurgens says, Denise was "a force of nature. Driven, passionate, energetic, funny, with a super sharp wit. She was able to tell her story over and over again and not have it lose an ounce of impact, because it came from the heart every time."
Jurgens says 10 women in Denise's family have been diagnosed with breast cancer and that four have died of the disease. Denise was dedicated to doing everything in her power to prevent her daughter from battling the disease. It is for this reason, she says, that the organization has decided to proceed with its upcoming Race For the Cure run this Sunday despite the tragedy.
"I asked the entire team if we needed to cancel, and they all said Denise would be so mad if we did. We're going to try to honor her by being as tough as she was."
Jurgens pointed to a testimonial Denise wrote on the organization's website about why she fights for a cure: "Why I fight? I fight for the little girl who wakes up every morning with a smile on her face. I fight for the little girl who gives me tight hugs and calls me mommy. I fight for the little girl who loves to draw butterflies, swim like a fish and play softball. I fight for Regan, my daughter."