Law enforcement officials in Texas say Haggerty was driving on Highway 380 near the city of Decatur in Wise County around 2:30 AM Friday ... when his car went off the right side of the road and hit a culvert, according to local reports.
Cops say Haggerty's vehicle flipped and hit a fence before coming to a halt. Emergency responders rushed to the scene, where Haggerty was pronounced dead.
Haggerty is a Texas hoops legend -- he was a high school star out of Houston ... and played 4 seasons at Baylor University, leading the NCAA in assists during his senior year.