Officials state that at least one person was killed and 12 others were injured during a shooting at a Halloween party in Oklahoma City early Saturday morning.

The shootout occurred at 12:30 a.m. CDT while outside of Patty’s Event Center in southern Oklahoma City after two groups of attendees began arguing; several people began shooting, while the argument spilled outdoors. Oklahoma City Police Capt. Valerie Littlejohn told reporters that a “disturbance” at the events center where the party was being held led to multiple shots being fired inside and outside the building, but it is unclear what the disturbance was that led to the shooting.

Oklahoma City Mayor David Holt confirmed that the incident included at least 13 total victims and is being investigated by local police detectives, and two adults have been arrested in connection with the mass shooting. Mayor Holt said in a post on Facebook: “Recent shootings in our city fit a familiar pattern — young men (boys, really) making terrible decisions with grave consequences. Boys whose brains are literally still forming don’t always respond rationally to the things that would deter you and I.”

Per ABC News, the names and ages of those involved in the incident have not yet been released. Police officials said they will release a statement regarding the mass shooting on Monday.

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