As Americans marked Easter Sunday amid the challenges of the coronavirus pandemic, the South faced a new menace.

A dangerous storm system that produced at least 13 radar-confirmed tornadoes battered Mississippi and Louisiana on Sunday night, killing at least seven people, damaging homes and other buildings and leaving more than 60,000 customers without power across the two states.

The fatalities were reported across four counties in Mississippi, according to local authorities. Mississippi Gov. Tate Reeves declared a state of emergency.

"This is not how anyone wants to celebrate Easter Sunday," Reeves said on Twitter. "As we reflect on the death and resurrection on this Easter Sunday, we have faith that we will all rise together."

As the storms began to move out of Mississippi, some residents may need to prepare for flooding after some areas received up to seven inches of rain on Sunday, said Eric Carpenter, a meteorologist with the National Weather Service in Jackson.

While the storm system will start to weaken on Sunday night, AccuWeather meteorologist Alan Reppert told USA TODAY that parts of Arkansas and Tennessee should prepare for especially strong winds.

More than 120,000 customers were already without power in Arkansas late Sunday, according to poweroutages.us.

Photos of damage began circulating on social media, from down trees and power lines to damaged barns and flattened homes. At one point during a Facebook Livestream, a NWS meteorologist used the phrase "deadly tornado" five times in less than 30 seconds. They repeatedly begged people to take cover, warning the coming tornadoes were "violent" and "catastrophic."

The National Weather Service reported tornadoes over the northwest and north-central parts of Louisiana. The city of Monroe said the storm damaged commercial buildings and homes in multiple neighborhoods.

Nearly 39,000 customers were without power in Louisiana, as well as more than 22,000 in Mississippi, according to poweroutage.us.

Louisiana Gov. John Bel Edwards also declared a state of emergency.

The storms were expected to move through the Mid-Atlantic and parts of the Northeast and the Eastern Seaboard into Monday, Accuweather said.

Adding to the unprecedented nature of the day: the question of whether or not to open community storm shelters. The decision is usually made at the county or local level. But because federal and state public health officials are mandating people stay at home and avoid gathering in groups larger than 10, the equation is complicated.

In a video message posted on the Alexander City, Alabama, Facebook page, Mayor Thomas Spraggins said Saturday that people needed to find a safe place on their own since public buildings wouldn’t be open as shelters because of the pandemic. “I’ll be praying for everyone to have a safe and happy Easter,” he said.

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But a statement from the city’s police department said shelters would be opened after all. Temperature checks would be performed and gloves and masks were being provided to anyone entering.

The initial decision against opening shelters was at odds with a message from Gov. Kay Ivey.

“Both the National Weather Service and the State Public Health Department remind Alabamians that the use of shelters and other resources take precedent, should the need arise,” Ivey said in a statement Saturday.

The Mississippi Emergency Management Agency said in a tweet Saturday that shelters would be open and encouraged residents to wear masks, use hand sanitizer and stay 6 feet apart.

If tornado shelters aren't open, experts advise residents to take cover in their houses as best they can.

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Residents should seek protection in bathrooms with no exterior walls, stairwells or a basement, AccuWeather meteorologist and emergency preparedness specialist Becky DePodwin said.

The "main point is to put as many walls between you and the exterior walls,” she said.

Contributing: Steve Kiggins, Doug Stanglin and Doyle Rice, USA TODAY; Sarah Fowler and Wilton Jackson, The Clarion Ledger (Jackson, Miss.); The Associated Press