Deputies say the incident happened around 2:50 a.m. in the 11500 block of Huffmeister.
According to the sheriff's office, the child's mom had reported her daughter, who she said has autism, had left the house.
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The child reportedly wandered into the street and was hit by a Nissan Murano that was traveling north on Huffmeister. The driver of the vehicle, a 49-year-old woman, stopped immediately and called 911.
The driver did not show signs of impairment and is cooperating with authorities.
Authorities say the 8-year-old suffered critical injuries and was taken by LifeFlight to the hospital, where she is currently in surgery.
@HCSOTexas units responded to the 11700 blk of Easterling Dr (Cypress North Houston/290 area). An Autistic child (9 yrs) wandered off from home and was struck by a vehicle. Lifeflight responded & transported. She sustained a head injury and is in unknown condition. #HouNews— Ed Gonzalez (@SheriffEd_HCSO) October 17, 2019