The weather service earlier reported water entering a Walmart store in southern Nashville with cars in the parking lot submerged up to their windows.

Police believe Hammond was "swept away by flood waters after getting out of his car that had become stuck on Flintlock Ct," near the Nashboro golf course, the MNPD said.

At least 15 people were rescued from an apartment complex after a building was damaged by a mudslide, the fire department said. Two of those rescued were taken to local hospitals with non-critical injuries.

The fire department said it also rescued about 40 dogs from a pet day care facility called Camp Bow Wow.

Rainfall totals across the middle Tennessee region since Saturday ranged from 4 to 8 inches, the NWS said. The Brentwood area of Nashville may have received 7 to 9 inches of rain, according to radar rainfall estimates.

The fast-falling rain inundated several rivers, creeks and streams, forcing them to breach their banks. Moderate-to-major river flooding was ongoing across the region Sunday morning.

The Cumberland River, which flows through downtown Nashville, was expected to reach its flood stage, which is 40 feet, just after 1 p.m. local time Sunday and peak at 41.9 feet shortly after midnight, according to Nashville Mayor John Cooper.

First responders are working with the Red Cross to walk creek beds and canvass affected neighborhoods, Cooper said.

In Williamson County, south of downtown Nashville, emergency crews responded to more than 34 swift water rescue calls from both vehicles and homes, Emergency Management Director Todd Horton said during a virtual news conference early Sunday. More than 50 roads were closed across the county.

Eight homes were struck by lightning during the storms, Horton said.

The Brentwood Fire Department was going door-to-door Sunday to check on residents who live near the Harpeth River, Brentwood City Manager Kirk Bednar said. Emergency officials conducted multiple water rescues of those trapped in their homes.

The flash flooding is expected to recede as the rain ends Sunday morning, but the river flooding will take more time to clear. Several rivers will not fall below flood stage for the next 24 to 48 hours.

The next chance for rain across Tennessee and Nashville will be from Tuesday night into Wednesday, CNN meteorologist Haley Brink said.

Tornado damage reported

There were also reports of possible tornado damage in the wake of the storm system.

Late Saturday afternoon, radar showed possible twin tornadoes in middle Tennessee, about 80 miles southwest of Nashville -- one near Linden and the other just east of Lexington. Two houses were "extensively damaged, one of which was destroyed" by a tornado Saturday evening in Middlefork, near Lexington, Henderson County Sheriff Brian Duke told CNN.

Several structures and homes were also damaged Saturday night when a tornado moved through Rusk County, Texas, according to David Chenault, spokesperson for the Rusk County Office of Emergency Management.

"We have had quite a bit of damage in the Mount Enterprise area of Rusk County," Chenault said.

Most of the roads in that area were blocked by downed trees, the spokesperson said, and utilities are out. The NWS has not officially confirmed any tornadoes in Mount Enterprise but a tornado warning was in effect around 7 p.m., when the damage happened.