Rajiv Singh says that his wife, Sunita – a mechanical engineer at an oil and gas company in Houston – usually leaves the house early enough to get to work by 6:30 a.m.
On Monday, her normal route was blocked off due to the city's major flooding, so she took a detour. Sunita's car quickly became submerged in water near the split off of Highway 59 and 610.
"Our phone call will linger in my head for a very long time, it was so brief, only 15 seconds long," Rajiv tells PEOPLE. "She called me around 6:47 a.m. and mentioned she was in a little trouble. She had driven into water and it was all around her, she had no idea how deep it was."
"She said she saw flashing lights, so she believed rescuers were there. And I was counting on that."
The grieving husband didn't realize his wife's car, along with another vehicle, had become completely stranded – eventually sinking into the flood waters.
Rajiv tried calling Sunita back after their short conversation – but she didn't pick up the phone.
"Her death is a horrible irony to me, because my wife's whole philosophy about life is to stay safe," Rajiv tells PEOPLE. "If a cup was too close to the edge of a table she got upset."
"If she had had any idea what she was getting into, she wouldn't have driven into the water. She was very perceptive."
Authorities confirmed that the drivers of both vehicles drowned in their cars, reports KHOU.com.
Sunita leaves behind her daughter Oshin, 23, and her two stepsons with Rajiv – Raghav, 19, and Gaurav, 15.
"The boys are crying and avoiding talking about the tragedy," says Rajiv. "And for me, I am moving like a robot. The gravity of the situation hasn't hit yet, but when it does I will have to make sense of it all."
Rajiv says Sunita was "cheerful, full of life and a hard worker."
"Most of all, she was a great mother, wife and human being," he says.
Officials have started pumping at the 59/610/Westpark interchange so they can see if any cars/people were trapped. pic.twitter.com/TmfjdbnjtU— Jace Larson, KPRC (@jacelarson) April 19, 2016
Rajiv hopes Houston city officials can come up with a solution to fix the sections of Houston Highway that are prone to flooding – like the split between Highway 59 and 610 where his wife died.
"[Houston] needs to prevent people from [driving into floods]. You need to have a good system to prevent people from going into those death traps or have some level control barricade as soon as the water level rises," he says. "That is not high-tech, that is fairly easy."
"I'm hoping that by going public, people will notice the need for change. I hope this gains traction in honor of my wife."
The National Weather Service has issued a flash flood watch through Wednesday morning. At least five fatalities have been reported since Houston began experiencing major flooding late Sunday night.
"Avoid travel in and around flooded areas," the warning reads. "Most people who die in flash flooding will die in their vehicles. If in a flooded area stay where you are ... at home or at work. Never drive into a flooded roadway. Turn around don't drown!"