NBC affiliate KPNX of Phoenix reported that the restaurant El Camarón Gigante was holding a Cinco de Mayo party at the time.

A fatal mass shooting in Glendale was isolated, police said. And it's one of dozens in the U.S. so far this year. But reputational concerns remain.

Three people were killed and five others were injured in a shooting Sunday evening at a restaurant in Arizona, Glendale police spokesperson Moroni Mendez said.