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

The fatal shooting Sunday night at a restaurant and event venue in Glendale, Arizona, was an “isolated incident that involved individuals that were known to one another,” the city manager’s office said in an update Monday.

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.