Reports in France said one woman who lost her husband in the terror attack also lost both her parents in the weekend's floods.
A military officer walks through a damaged street due to heavy rain falls, flash floods and violent storm that hit Aude department overnight in Villegailhenc, France, Oct. 15, 2018.
A spell of torrential rain resulted, with Carcassonne recording 70mm of rain in just three hours.
In what the local weather agency said was some of the worst flash floods the Aude river has seen in more than a century, the heavy rainfall brought raging torrents that engulfed homes and swept away cars.
A sixth person also died in the department, local authorities said, but gave no further details.
At least 12 people have died, including a nun, after the equivalent of up to seven months' rain fell in just a few hours in south-western France.
There were several deaths in the town of Trebes, which sits between a canal and two rivers, including the Aude. The ministry said it revised the figure later in the day after realizing some victims had been counted twice. Officials say it hasn't reached such high levels since 1891.
Interior Ministry spokesman Frederic de Lanouvelle said one other person is missing and five others are seriously hurt.
The worst-hit town was Trebes, east of the medieval walled city of Carcassonne, where nine people were killed.
Four other people were reportedly killed in nearby Villegailhenc, where the water reached the first-floor windows of homes. Siguet, 17, posted video of a ripped-up road where a bridge used to stand. Schools in the area were closed and residents were told to stay at home. A Villegailhenc resident described for French news channel BFMTV how little time there was to escape.
"We have about 15 communes in a delicate situation", Thirion told The Local. So, what do I do?
"She thought she was safe behind locked doors and windows, but the water burst in". I go to the kitchen, I open the door.
"There's water everywhere in the house. I was terribly afraid".
Television images showed waters coursing through towns and villages, with cars stranded in the floodwaters.
The French government rushed hundreds of rescue workers into the flood zone and helicopters buzzed overhead.
French President Emmanuel Macron has extended the "solidarity" of the French nation to residents of the southwestern region struck by flash flooding and to the families of people who died in the disaster. The official asked for anonymity because he was not authorized to speak publicly.