A sudden and destructive storm tore through southern Wisconsin on Friday, killing three people after a boat overturned on Geneva Lake during the heavily traveled Fourth of July holiday weekend.

The incident happened as a powerful storm system moved into Walworth County at about 12:10 p.m., bringing dangerous conditions to the area.

As the storm intensified, dispatchers began receiving urgent 911 calls reporting that a boat had capsized on Geneva Lake and that several people were in the water.

A City of Lake Geneva police boat and officers with the Geneva Lake Law Enforcement Agency were able to pull seven people from the lake, but three others did not survive, Walworth County Undersheriff Tom Hausner said at a news conference.

Emergency responders later recovered the victims’ bodies.

Officials have not publicly identified the three people who died. Sources told CBS News Chicago, however, that all three victims were children.

The Geneva Lake Law Enforcement Agency and the Wisconsin Department of Natural Resources are jointly investigating the capsizing.

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Hausner noted that Walworth County’s year-round population is about 106,000, but that number can climb to more than 200,000 during busy holiday weekends, including the Fourth of July.

“Our resources, not just the sheriff’s office, but all law enforcement resources and fire and EMS are stressed, and this compounded that to levels unprecedented,” Hausner said.

The sheriff’s office initiated an emergency call-in of all off-duty deputies and requested mutual aid from Rock, Kenosha and Jefferson counties and the Wisconsin State Patrol and DNR.

City of Lake Geneva Mayor Todd Krause issued an emergency declaration at 12:18 p.m. after the high winds and heavy rains knocked down power lines, shattered trees, damaged buildings and left cars crushed.

Numerous storm-related injuries have been reported, forcing area hospitals to enact diversions due to the overwhelming volume of patients.

The Geneva Lake Law Enforcement Agency, City of Lake Geneva Police Department, Walworth County Sheriff’s Office and Walworth County did not immediately respond to additional inquiries from Fox News Digital.

The Wisconsin Department of Natural Resources referred all inquiries to the City of Lake Geneva Police Department.