(CNN) -- As temperatures soared Monday, the cool water of Shreveport, Louisiana's, Red River lured a group of family and friends to its banks.
In an effort to cool off, one of the teens wandered into the shallow part of the river.
At some point he slipped into deep water and started to drown.
So six more teens went to his rescue.
Only one made it back to shore.
Shreveport, Louisiana, Fire Chief Brian Crawford said as soon as the first teen was in trouble, the others instinctively rushed to help.
"Whether you can't swim or don't swim ... you're just gonna go and do what you think you have to do," he said.
The parents stood helpless on the shore and watched as their children struggled and eventually slipped under the water. The adults could not swim either.
"Imagine watching your child drown and not being able to do anything," Crawford said.
Brothers Litrelle Stewart, 18; Latevin Stewart, 15; and LaDairus Stewart, 17; and siblings Takeitha Warner, 13; JaMarcus Warner, 14; and JaTavious Warner, 17 died.
African-American children drown at a rate almost three times higher than white children, according to Make a Splash, a national child-focused water safety initiative created by the USA Swimming Foundation.
But swimming officials said the key indicator is not race, but family -- children from nonswimming households are eight times more likely to be at risk of drowning.
The divers said the river bed drops from a shallow area to about 28 feet deep. The six teens were found within 20 feet to 30 feet of each other. Though because the divers were combing through "black water," the recovery took more than two hours.
Crawford said divers were committed to retrieving the bodies, even as the night closed in.
"I'm a parent, and I can't imagine I've lost my child and then they spend the night at the bottom of a river," he said.
Authorities are trying to construct the timeline of events. Shreveport Mayor Cedric Glover said he met with the lone survivor Monday night and he is "having a rather difficult time right now, and I don't want to have any more burden placed on him or added guilt than he's already handling right now."
Police officers have spent time this summer issuing tickets, warnings and even creating barriers in an effort to keep people away from the swift Red River in Shreveport. The area is a popular spot for boaters who tie up and barbecue. But it can be a death trap for someone without a life jacket who can't swim.
"What is ironic is the Shreveport Police Department through July worked a series of enforcements to discourage people from parking and accessing that part of the river," said Glover, adding that the city does not allow recreational activities, including swimming along the banks of the river. Only boaters are allowed.
The fire chief said to honor the children's memory, he wants the public to be aware of the river's inherent danger.
"Somebody's going down to that river today, and they don't need to get in the water if they don't know how to swim or have a flotation device."
CNN's Shawn Nottingham contributed to this report.