Eight children, aged from one to 14 years old, were killed in a shooting in Shreveport, Louisiana, which police are describing as a "domestic disturbance".
Officers said the shootings occurred about 05:00 local time (10:00 BST), when a single gunman shot 10 people.
Police chased and killed the suspected shooter as he was fleeing, reports BBC.
"We have hurting families, we have hurting police officers, coroners' personnel," Shreveport Mayor Tom Arceneaux said. "This affects the entire community, so we all mourn with these families."
Police did not identify the gunman or the victims, but said some of the children were related to the deceased man.
"This is a tragic situation - maybe the worst tragic situation we've ever had in Shreveport," the mayor added. He asked for prayers for the families and the city.
Police said the shooting took place at two homes on the same block and a third residence in the neighbourhood.
Shreveport Police Corporal Chris Bordelon said officers attended a home shortly before 06:00 local time and found the children.
"All of the deceased in this case are juveniles," Bordelon said.