A mother with her 9-year-old son in the backseat of her car intentionally drove through the construction barricades just north of the bridge and into the water at a high rate of speed, according to Interim Hickory Creek Police Chief Carey Dunn.
Three strangers, Jeff McMart, James Espita and Allen Harrison, were sitting in traffic on I-35E when they saw the splash the car made in the water.
The three men jumped into the lake to pull the woman and child out of a rapidly sinking sedan.
Hickory Creek investigators say what first appeared to be an accident is now determined to have been an intentional act by the mother to drown her son and herself.
Police say the mother was undergoing a psychological evaluation on Monday and her son is safely in the care and custody of other family members.