At about 4pm, officials were called to the 4000 block of Lexington near Murphy Road, where the two victims were found in the water at the American Legion Park.
Besides the bystander, three emergency workers, who were in the area at the time, helped to rescue the victims.
"They went into the water, brought both of the subjects out. We immediately began treating them," said Jon Wheeler with the Missouri City Fire Department. "The female was near the kayak or hanging onto the kayak and the other subject was out into the water, a little bit further away."
Missouri City officials said the two victims were 50-year-old Steven George Bouton and his teenage step-daughter. They say neither were wearing life jackets when they were pulled from the lake.
Both victims were transported to an area hospital. Bouton later died from his injuries.
"Our Departments are saddened by Mr. Bouton's tragic death and extend our sincere condolences to his family," Police Chief Joel Fitzgerald and Fire Chief Russell Sander said in a release.
Bouton's step-daughter survived the accident. At last check, she was stable. Her name and age have not been released.
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