A South Dakota man shot and killed three people and critically wounded a fourth person before taking his own life at a residence on a Native American reservation, law enforcement officials said Saturday.

Local police cooperating with Sisseton-Wahpeton Sioux Tribal Police had launched an early morning manhunt for the shooting suspect but later said the gunman was among the dead found inside a residence in the city of Sisseton, on the Lake Traverse Indian Reservation.

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“The Division of Criminal Investigation has located and identified Colter Richard Arbach, 22, Sisseton, as one of the deceased individuals at the scene of the shooting incident,” a news release from the state attorney general’s office said.

Arbach appears to have died from a self-inflicted gunshot wound, the release said.

The identities of three other people killed in the incident were not released. A fourth person was sent to hospital with critical wounds, law enforcement said.

The motive behind the killings was not yet clear.

(Reporting by Victoria Cavaliere; Editing by Raissa Kasolowsky)