Story highlights A woman swept away as firefighters tried to rescue her is found dead, spokesman says

Her car was in the water when it struck her would-be rescuers' boat

She's the second woman in San Antonio to die due to the flooding

Several rivers and creeks in and around the Texas city are well above flood stage

Two women died Saturday -- one of them after being swept away moments after being inches from her would-be rescuers -- due to raging floodwaters in San Antonio, which braced for yet more drenching rains.

At one point Saturday, a storm and subsequent floods had knocked out power to about 12,000 customers and spurred the closure of dozens of streets in the Texas city and the surrounding county, authorities said.

Scores of people had to be evacuated due to floods and other issues, and Fire Chief Charles Hood noted there had been about 250 water-related calls -- in addition to ones for things like medical emergencies, accidents and more -- in the first 15 hours of Saturday.

The greatest concern had to do with people getting too close to fast-moving, deceptive and unpredictable floodwaters.

"We're asking folks to observe low-water crossing (warnings), to use common sense and to stay off the road if possible," Mayor Julian Castro said.

The first confirmed fatality -- a woman around age 30 -- was reported around 7:30 a.m. (8:30 a.m. ET), and her body was about three hours later, police Chief William McManus said.

Some time later, an older female driver went into water that was 4 feet above flood markers. Firefighters got to her vehicle and broke a window -- with one firefighter cutting his hand -- Hood explained. Then, as the would-be rescuers tried to get her from her vehicle, "the currents changed and washed that vehicle away," the fire chief said.

The woman's car had rolled on top of rescue boat, forcing out the firefighters who'd been in it, fire department spokesman Christian Bove later explained. By the time the firefighters were able to climb back into the boat, her car had become submerged in about 25-foot deep water and was gone.

Hood characterized authorities' subsequent efforts to find this woman as "a body recovery."

Described as being in her late 60s, the victim was found dead inside her vehicle around 6:45 p.m., Bove said.

"You can imagine how emotionally spent you are to try to rescue somebody, you're face-to-face with them, and then they're washed away," Hood said of his distraught firefighters, who'd gotten so close to rescuing the woman only to lose her.

The chief warned more people may be missing and perhaps dead. Firefighters happened to spot this woman going into the water before they rushed to rescue her; there may be others, Hood pointed out, who firefighters or others don't see get trapped in floodwaters.

"Turn around and don't drown," multiple officials repeated at a Saturday news conference.

The problems began with torrential rains late Friday that continued into Saturday, triggering flash-flood warnings across South Texas.

The weather was windy and wet and included a reported tornado on Friday in Bexar, just west of San Antonio, that knocked down trees and power lines and caused "minor building damage," according to the National Weather Service

San Antonio International Airport received 9.57 inches of rain Saturday morning alone, CNN meteorologists said.

The city's Leon Creek was at 27.1 feet at 2:16 p.m. Saturday -- well above the flood stage of 15 feet.

"Disastrous flooding puts near 7 feet of flow in buildings in the jet engine test facility at Kelly AFB," the National Weather Service said . "Secondary and primary roads and bridges are severely flooded and dangerous to motorists above Highway 90 to below (Interstate 35)"

Flood warnings have also been issued for the San Antonio River, Medina River and Salado Creek, all of which are above flood stage. The weather service forecast that storms "could produce heavy rainfall" sometime after

In an interview with CNN affiliate KENS , San Antonio resident Mary Alice Galicia described how water enveloped her house.

"It was underwater 20 minutes ago," she said earlier Saturday. "I came over here. I own the property, and my daughter said that she couldn't get to her car. Her car's all flooded. The property -- the water's all swarming through the whole house. I just came over to check to see what I could do, but there's nothing that I can do right now."

Galicia doesn't have flood insurance because she "never imagined this would happen," she said.

"But it's not stopping. I thought it was gonna stop," she said about the water damage.

San Antonio's previous record flooding in 1998 was devastating, caused by heavy rains throughout south Texas and by a plume of moist air from Hurricane Madeline off the Mexican west coast. A total of 11 people died in San Antonio that weekend, with property damage estimates at $750 million, a city report said.