Las Vegas police were dispatched to the Walmart parking lot late Thursday in reference to a report of people in vehicles shooting, Chief Christian Montaño said.
No one appears to have been injured.
Montaño said officers responded in less than a minute. The suspects, however, had already left the scene.
As of Sunday morning, they had not been located, though officers were going over store video surveillance footage.
Two casings were found on the ground, Montaño said.