At least three people were killed in a shooting inside a Walmart store Wednesday in suburban Denver, where police said they had not yet taken anyone into custody.

Police in Thornton, Colorado, did not immediately release any information about the circumstances of the shooting or who was responsible for the gunfire.

Two men were killed in the shooting. A women, who was injured in the shooting, was taken to a hospital where she later died, Thornton Police Department said on Twitter.

“Detectives currently reviewing security footage & witnesses being interviewed for assistance with suspect(s),” police said on Twitter.

No one had been taken into custody, police said.

The situation appeared potentially ominous from authorities’ initial reports.

About an hour after the initial alert, police said on Twitter that the threat of gunfire had ended at the store, which was surrounded by police and fire crews.

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