A California man found driving a vehicle carrying his mother’s body has become a “party of interest” in the woman’s death investigation.

Tosten Walsh Lommen, 30, is being held at the Pennington County Jail in lieu of a $2.5 million bond on charges including aggravated eluding and driving under the influence. South Dakota police arrested him on New Year’s Day following a high-speed chase on Interstate 90, and discovered a woman’s body in the back of the SUV.

The woman was identified as Walsh Lommen’s mother, 58-year-old Michelle Walsh of Palm Springs, Calif. South Dakota authorities announced Monday that her death involved foul play.

“Preliminary autopsy results indicate blunt trauma injury to her head and hemorrhage anterior neck musculature,” state attorney general Marty Jackley said in a release. “This confirms this is a homicide.”

The Palm Springs Police Department, which is involved in the death investigation, said it’s looking into Walsh Lommen’s possible role in his mother’s death.

“I don’t know whether they deem him a suspect in this case yet or not," Sgt. William Hutchinson, the police department spokesman, said in an interview Monday. "But I can definitely tell you he’s certainly a party of interest.” Palm Springs police are currently not looking into other suspects, he said.

California law enforcement officers are now trying to determine whether Walsh's death happened in Palm Springs, and whether her son should be criminally charged. His address is listed as Santa Cruz, Calif.

If the answer to both questions is yes, Palm Springs authorities "will assume control of this investigation," Hutchinson said, adding that they would then seek Walsh Lommen's extradition from South Dakota.

The South Dakota Attorney General’s Office said as of Monday, no additional charges have been brought against Walsh Lommen.

According to Pennington County court documents, Walsh Lommen caught the state Highway Patrol’s attention around noon Jan. 1, when a trooper saw him heading east on I-90, in Lawrence County, “at speeds in excess of 100 mph.” The trooper failed to get him to stop.

Somewhere in Meade County, another trooper registered Walsh Lommen’s SUV traveling at 118 mph. The highway patrol and Rapid City police laid out spike strips, which deflated the vehicle’s front tires, bringing it to a stop in a ditch along I-90 within Rapid City.

Walsh Lommen reportedly ran from the vehicle, but two troopers grabbed him as he was trying to go over a chain-link fence. A search of the SUV revealed “a female body in the rear of the vehicle wrapped in a blanket,” reads a patrol trooper’s statement.

Troopers also located prescription medication for Walsh Lommen, as well as credit cards belonging to Walsh, whose name also appears on the vehicle’s registration.

A preliminary breath test on Walsh Lommen showed he had a blood alcohol content of .142, according to the statement. That is almost twice the threshold for drunken driving in South Dakota, which is .08 BAC.

Aggravated eluding is a felony punishable by up to two years in prison. Walsh Lommen’s three other charges are misdemeanors, each carrying a maximum penalty of a year in county jail.

He is scheduled to return to court for a preliminary hearing on Jan. 17

Contact Tiffany Tan at tiffany.tan@rapidcityjournal.com.