ANTLERS, Okla. - Four people have been arrested in connection with an Antlers homicide investigation, but authorities say they are still searching for the adult male victim.

The investigation began Sept. 2 after the Pushmataha County Sheriff's Office received a report from a caller who said they had witnessed a homicide.

Deputies responded that morning to a residence in the 100 block of Northwest East Street in Antlers. The Oklahoma State Bureau of Investigation was asked to assist, and deputies and OSBI special agents began processing the scene.

Investigators initially identified three people of interest, and the Pushmataha County District Court subsequently issued arrest warrants for David Basham, 29; Bonnie Simpson, 28; and David Osterdock, 25.

Osterdock was located and arrested by Idabel police on Sept. 8. He was booked into the McCurtain County Jail on a complaint of accessory to murder.

Two days later, the U.S. Marshals Service arrested Simpson. She was also booked into the McCurtain County Jail on an accessory to murder complaint.

Basham was located in Wisconsin on Sept. 11 by the U.S. Marshals Service. He was booked into the Sheboygan County Jail on a first-degree murder complaint.

As the investigation continued, OSBI agents identified a fourth suspect, Chelsea Driver, 42.

Special agents located and arrested Driver in Pushmataha County on Sept. 21. She was booked into the Pushmataha County Jail on an accessory to murder complaint.

Despite the four arrests, investigators have not located the adult male they believe was killed. Authorities have not released his identity or disclosed what evidence led them to conclude a homicide occurred.

Anyone with information about the case or the victim's whereabouts is asked to contact the OSBI tip line at 1-800-522-8017 or tips@osbi.ok.gov.

The U.S. Marshals Service, Idabel Police Department, McCurtain County Sheriff's Department and Pushmataha County Sheriff's Office have assisted OSBI with the investigation.