Shootouts and fires created what has been described as a “night of terror” for residents of a southern Sonoran city.

For more than an hour Wednesday night, neighborhoods in Empalme experienced continuous gunfire by criminal groups that also set a bus and a convenience store ablaze.

Videos and photos circulated on social media depicted a scene of chaos that Manuel Hoyos said are the result of a crisis of sustained violence in the region.

"Guaymas, Empalme, they continue to be the epicenter in Sonora," said Hoyos, head of the security-focused citizen group Observatorio Sonora por la Seguridad. "It's not new. But what we see is that the violence just hasn't stopped. And it's become a sustained crisis of violence."

Empalme is among five Sonoran cities selected for 2019 pilot program that replaced police heads with military leaders in an effort to combat rising violence. Instead, Hoyos said, increased militarization has only made the problem worse, with murders and disappearances continuing to rise.

On Thursday, state police announced four people were arrested for their alleged involvement in the shootout, but released no other information about what they described in a press release as "acts of vandalism."