A man crashed his SUV into a car carrying his ex-wife and three children at a Mankato park, then shot and killed the woman, carjacked the SUV of a Good Samaritan who tried to help, and fled with the children in the stolen vehicle, authorities said Monday.

Police identified the woman as Svetlana Vladimirovna Munt, 32, of Mankato, the former wife of the suspect, a 33-year-old Burnsville man who was being held on suspicion of second-degree murder but had not been charged Monday. He was expected to make his first court appearance Tuesday.

Investigators would not say how Vladimirovna or the suspect were related to the children. They said the investigation continued Monday, but the case had been turned over to the Blue Earth County attorney’s office.

Police said in a statement that officers responded to a call of shots fired just before noon Sunday at the Rasmussen Woods Nature Area. At the scene they found an SUV that had collided with a car and pinned it against some trees. The SUV’s engine was running, the transmission was in gear, and a tire was spinning on the pavement, smoking as it disintegrated. The woman was found dead inside the car.

A person who saw the smoke had stopped to help, but the suspect stole that person’s SUV and drove off, the statement said.

A short time later, a Blue Earth County sheriff’s deputy who just happened to be in the right place at the right time stopped the vehicle on a dead-end gravel road, arrested the suspect without incident and recovered a gun, Capt. Rich Murry of the sheriff’s department told reporters.

The three children were put in protective custody.