(CNN) With his girlfriend Keila seated next to him and her three children in the back, Christopher Rodriguez was driving on a cool, clear Saturday night.

The family of five had just visited Keila Ruby Flores's brother in Round Rock, Texas, and was headed north to Waco on Interstate 35. Without warning, a large rock from a railroad track overpass smashed into the vehicle's windshield and hit Flores.

"All of a sudden, something just strikes the window. It's an explosion," he told CNN affiliate KWTX . "I look over and I see Keila and she's just laying there unresponsive. I'm shaking her, trying to wake her up, (but) she was unresponsive."

Rodriguez pulled onto an access road, called police and began to perform CPR, but it wasn't enough. Flores, a 33-year-old mother of three, was rushed to a nearby hospital and died the next morning, Temple Police said.

No suspects

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