The victims ranged in age from one to about 14 years old, Shreveport police spokesman Chris Bordelon said.
A total of 10 were shot and some of the children were related to the suspect, Bordelon said.
The gunman later died after a chase with officers who fired at the suspect, Bordelon said.
The suspect stole a car while leaving the scene of the shootings and was followed by police, according to Bordelon.
Police did not release the name of the suspect but did say he was an adult male.
The shootings were the result of a "domestic disturbance," Bordelon said.
Officials said they were still gathering details at the crime scenes south of downtown Shreveport - the two homes and a third location.
"This is an extensive scene unlike anything most of us have ever seen," he said.
At a news conference outside the residence where one of the shootings occurred, officials appeared stunned, requesting patience and prayers from the community as they sorted through multiple crime scenes.
"I just don't know what to say, my heart is just taken aback," Shreveport Police Chief Wayne Smith said.
"I cannot begin to imagine how such an event could occur."
"This is a tragic situation - maybe the worst tragic situation we've ever had," said Tom Arceneaux, mayor of the city in northwestern Louisiana with about 180,000 residents.
"It's a terrible morning."
Louisiana State Police say their detectives have been asked by Shreveport police to investigate.
It was the deadliest mass shooting in the United States since eight people were killed in a Chicago suburb in January 2024, according to a database maintained by the Associated Press and USA Today in partnership with Northeastern University.
17°C