Melissa Police are investigating the cause of a fatal crash on U.S. Highway 75 last Sunday after a Sherman family’s vehicle veered off the roadway, killing a 9-year-old girl and seriously injuring her relatives.

Asst. Chief Roger Thornhill said the wreck occurred at approximately 3 a.m. on Sunday in the northbound lanes of U.S. Highway 75. Thornhill said the vehicle, which was driven by a male family member, was approaching Throckmorton Creek when it began to drift off the freeway.

“The vehicle went over into the center median, continued for a distance and then went down into the lower area of the creek bed, where it struck a bridge pillar,” Thornhill said.

R’Niyah Williams was pronounced dead at the scene. Thornhill said Williams’ pregnant mother sustained serious injuries in the crash, as did three other children and the male driver. The four surviving family members were transported to area hospitals for treatment. Thornhill did not know their updated conditions Wednesday, but described their injuries as “incapacitating,” and added that they ranged from broken bones to severe trauma wounds.

Thornhill said the exact cause of the crash remains under investigation, including whether the driver fell asleep at the wheel. No other vehicles were involved in the crash.

“People need to plan out their activities of the evening ahead of time and if they’re out late, they need to be aware that fatigue may set in and affect their ability to drive safely,” Thornhill said.

In an emailed statement, the Sherman Independent School District confirmed R’Niyah Williams’ enrollment as a third grader at Neblett Elementary and said additional counselors would be available to students this week.

“R’Niyah Williams was (a) cheerful third-grader and will be remembered as a great classmate with a gentle spirit,” the statement read. “We extend condolences to her family, friends, and classmates during this time.”