Next-of-kin notification was still pending “because of a significant language barrier,” police said.
Authorities have a suspect in mind, but the Oklahoma State Bureau of Investigation (OSBI) is withholding the name for now to avoid endangering others.
“The suspect was inside that building for a significant amount of time before the executions began,” OSBI said in a news release on Tuesday.
“Based on the investigation thus far, this does not appear to be a random incident.”
State police said Tuesday the victims had been shot.
OSBI Captain Stan Florence said the previous day that authorities believe the suspect knew the victims, who were found dead Sunday night.
“They all know each other,” Florence said.
“Don’t know if they’re related, or if they’re coworkers, but certainly these individuals were, we believe, all familiar with each other.”
Authorities have not identified the victims. The case is being investigated as a quadruple homicide.
The Oklahoma Bureau of Narcotics and Dangerous Drugs Control is also investigating the deaths.
The agency has targeted criminal growing and trafficking of marijuana for the black market in recent years. But agency spokesman Mark Woodward said Tuesday it was too soon to say that was a focus of this investigation.
“It being a marijuana farm, obviously Oklahoma state law requires that they have a licence from the Oklahoma Medical Marijuana Authority and from us,” Woodward said.
“One of the things we’re looking at is, is it obtained legally or was it obtained by fraud? So that’ll be part of our investigation.”
Porsha Riley, spokeswoman for the Oklahoma Medical Marijuana Authority, said there is an active licence for a medical marijuana growing business at the location.
None of the 14 marijuana growing operations in the Hennessey area responded to email inquiries from The Associated Press, and officials would not identify which one operated at the site of the shootings.
The Kingfisher County Sheriff’s Office initially responded to a reported hostage situation at the farm and requested help from state authorities, Florence said.
Police searched the property late Sunday and Monday, using drones and helicopters and on the ground, but did not find the suspect, Florence said.
“There’s a lot to unravel with this case,” he said. “It’ll take a little time for us to process it.”
In March, voters will decide whether to legalise recreational use of the drug.
Maryland and Missouri approved recreational marijuana in this month’s midterm elections, bringing the total number states that allow recreational use to 21. Arkansas, North Dakota and South Dakota voters rejected legalisation proposals in the midterms.