Neighbor Fazz Zainuddin told KPRC that police told Sheats to put down the gun, but she did not. When Sheats walked toward one of the bodies, a Fulshear police officer fired a single shot, killing her, according to Fort Bend County Sheriff Troy Nehls.
One daughter died in the street, and the other died after being flown to a nearby hospital, KPRC reported.
Sheats' husband and the victims' father, Jason Sheats, witnessed the killings, law enforcement officials said. Friday was his birthday, according to KTRK.
"It was a family argument that turned into a shooting, but we're still trying to put the pieces together," Nehls told the Houston Chronicle.
Buzzfeed reported that Sheats posted about guns on Facebook.
"It would be horribly tragic if my ability to protect myself or my family were to be taken away, but that's exactly what Democrats are determined to do by banning semi-automatic handguns," she posted in March.