Man with history of domestic violence admits to killing Billings mother of five

Over a dozen people sat in a Billings courtroom Thursday, some of them sobbing, and listened as a man admitted to killing a mother of five.

Shawna Hart’s children were among those in Yellowstone County District Court who witnessed Tanner Michael Grove plead guilty to murdering their mother less than two weeks after threatening them with a weapon. Hart was in the process of divorcing Grove, who had already served time in jail for assaulting her.

Hart’s death sparked outrage along with a flood of support for her friends, family and all local survivors of domestic violence, prompting the Billings City Council's pledge to review the city’s services for domestic violence survivors and its response systems to reports of partner and family member assault.

In court Thursday, the presiding Judge Mary Jane Knisely said it had only been 100 days since prosecutors had charged Grove with homicide. Such cases typically take at least a year to resolve, Knisely said, and repeatedly asked Grove if he was prepared to waive his right to a trial or even bargaining for a plea agreement with prosecutors.

“Yes,” Grove answered several times, his voice trembling throughout the hearing at the Yellowstone County Courthouse.

One of Hart’s sons sat at the front of the gallery. For nearly the entirety of Thursday’s 45-minute hearing, he didn’t take his eyes off Grove.

Sarah Kottke, who represented Grove alongside Joseph Zavatsky, stood next to Grove as she walked him through all of the specifics of the charges against him. Grove, handcuffed and dressed in jail garbs, admitted to each count against him, including deliberate homicide.

“Mr. Grove,” Knisely asked near the conclusion of Grove’s change of plea hearing.

“Yes?” he said.

“Returning to count one, deliberate homicide, how and where did you commit this offense,” she asked. “What did you do to cause her death, and where did it occur?”

“I used the airsoft pistol and … shot her,” Grove said, “on Rimrock and Zimmerman and I didn’t take her to the hospital.”

“You shot her and then went to Big Horn County,” Knisely said.

“Yes,” Grove said.

“How do you plead to deliberate homicide?”

“Guilty.”

Because Grove entered his guilty pleas without any kind of agreement with prosecutors, he faces up to maximum penalties for each count. For deliberate homicide, that means he could be sentenced anywhere from 10 years to life in prison. Thursday’s hearing concluded with Knisely scheduling the sentencing in November, then detention officers leading Grove out of court to return to YCDF.

On April 23, a friend of Hart’s reported her missing to the Billings Police Department, telling law enforcement that she last saw Hart the previous night getting into a Chevy SUV with Grove. Hart’s friend told law enforcement Hart had left her cell phone and her children at her residence when she climbed into the SUV.

At that time, Grove had a no-contact order in place prohibiting him from speaking to or meeting with Hart. Along with their ongoing divorce, Grove spent five months in jail following his conviction for misdemeanor partner or family member assault. A Billings Municipal Court judge sentenced Grove to a year in jail, with all but 150 days suspended. He left custody in mid-March of this year.

Less than two weeks after his release from the Yellowstone County Detention Facility, Grove threatened two of Hart’s family members with a high-powered air pistol while they were helping Hart move out of a residence.

Yellowstone County prosecutors subsequently charged Grove with felony assault and violating a no-contact order. By early April, Grove had two warrants for his arrest, but eluded law enforcement.

On April 24, a member of Hart’s family went to Billings police in person to report her missing. He showed officers texts over the previous week between Grove and Hart that court documents described as “turbulent.”

Data pulled from Hart’s phone showed Grove calling Hart at around the same time that Hart’s friend last saw her two days prior. BPD put out a missing person advisory for Hart, asking the public for help in finding her.

That same day, Billings police conducted a traffic stop on a vehicle driven by a known acquaintance of Grove. Officers pulled over a black Cadillac driven by a 28-year-old woman. Grove was sitting in the passenger seat and tried to run away. Police arrested Grove and booked him into YCDF.

Later in the afternoon, law enforcement found the Chevy SUV on a stretch of farmland in Big Horn County west of Hardin. Inside the SUV, they recovered Hart’s body. She’d suffered a penetrating wound to the head, according to charging documents. Surveillance footage showed the Chevy driving onto the property on April 23. The footage captured a man, identified as Grove, getting out of the vehicle, pulling a bicycle out of the rear and riding away. Grove would later admit to having stolen the bike he rode after killing Hart.

Grove initially pleaded not guilty to counts of deliberate homicide, burglary, tampering with evidence, two counts of assault with a weapon and two misdemeanor counts of violating an order of protection. He was arraigned in court in late April and has remained in custody since then, with his bond set at over $3.5 million.

In between Grove’s initial hearings and his changing his plea Thursday, Hart’s family and friends advocated on her behalf, taking their grief and outrage to the Billings City Council. Less than a week after Hart’s death, council planned multiple sessions in which its members discussed how the city’s social and law enforcement agencies responded to cases of domestic violence.

Those sessions concluded in early July, the Gazette previously reported, with Mayor Mike Nelson making a directive establishing a six-month committee with a focus on coordination of care and response, reviewing how the city’s services respond to domestic violence and finding what areas need improvement.

On Thursday, the same people who petitioned the City Council to improve local services for domestic violence survivors were present in the courtroom. 

While homicide cases in and around Billings have declined significantly in recent years, according to BPD data, arrests related to intimate partner violence have remained fairly consistent. Since 2021, according to past reporting from the Billings Gazette, there have been at least nine deaths in Billings related to domestic violence: seven women and two young boys.