Nashville Mayor John Cooper issued a “state of civil emergency” following an explosion that occurred downtown on Christmas Day, imposing a curfew that will not be lifted until Sunday.

“I have signed Executive Order 12 to issue a state of civil emergency proclaimed within the area bounded by James Robertson Parkway, 4th Ave north, Broadway and the Cumberland River,” the mayor announced Friday evening.

“A curfew will start at 4:30pm, Friday Dec 25. and be lifted Sunday, December 27 at 4:30pm,” he added:

According to Metro councilmember Freddie O’Connell, the curfew took many people by surprise:

Nashville Police Chief John Drake provided an update on Friday, noting that police were responding to a call of shots fired before hearing an evacuation warning on a loudspeaker.

He said:

This morning, around 5:30 a.m., officers responded to a call for shots fired in the downtown area, specifically 2nd and near Commerce. As officers responded, they encountered an RV that had a recording saying that a potential bomb would detonate within 15 minutes. Officers, upon hearing that, decided to evacuate the buildings nearby. So they began knocking on doors, making announcements, having emergency communications communicate with everyone to get people safe. Shortly after that, the RV exploded. We had one officer that was knocked to the ground. Another officer is fine.

Six officers  — Brenna Hosey, James Luellen, Michael Sipos, Amanda Topping, James Wells, and Sergeant Timothy Miller — have been recognized for evacuating people and saving lives ahead of the explosion.

As Breitbart News reported, the explosion is widely believed to have been intentional but “meant to limit casualties.” Human remains, however, have been found at the site of the blast, according to the Associated Press.