Four people killed at a marijuana growing facility in Oklahoma over the weekend were “executed,” authorities said Tuesday. 

The Kingfisher County Sheriff’s Office responded Sunday to reports of a hostage situation at the grow facility, outside Hennessey, about 55 miles northwest of Oklahoma City. A suspect entered a building where several employees were at about 5:45 p.m. and stayed inside “for a significant amount of time” before executing four people and critically injuring another, Oklahoma State Bureau of Investigation said in a release.

Officials found four killed, three men and a woman, who were all determined to be Chinese nationals, as was the injured victim, who was air flighted to a hospital.

The OSBI said Tuesday they had identified a suspect but that releasing the information would “put additional individuals in danger.” Bureau officials said an arrest warrant has been issued, local station KOCO 5 reported.

Officials have not identified victims, citing language barriers as causing a delay in notifying next of kin.

OSBI Capt. Stan Florence said the suspect is believed to know the victims, according to the Associated Press.

“This was definitely not random. This appears to be a very purposeful act,” Brook Arbeitman, a spokesperson for OSBI, told KOCO 5.

The medical use of marijuana is legal in the state of Oklahoma, and voters will weigh in on whether its recreational use should be legalized next year. Porsha Riley, a spokesperson for the Oklahoma Medical Marijuana Authority, said there was an active license for a grow business at the location, the AP reported. 

Contributing: The Associated Press