(CNN) A woman in Texas gunned down her two daughters -- killing both of them -- before a responding police officer killed the mother, authorities said.

Christy Sheats, 42, fatally shot daughters Taylor, 22, and Madison, 17, on Friday in Fulshear, west of Houston, according to the Fort Bend County Sheriff's Office.

After someone called 911, a Fulshear police officer shot the mother when she refused to put down her weapon, the sheriff's office said.

The daughters were found on the street with gunshot wounds. The older daughter died at the scene; the younger one at a hospital.

Deputies had previously told CNN that the older daughter was 19 but later corrected the age to 22.

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