Mr. Williams flashed his gun, stole the couple's car keys and attempted to back up the Honda, the detective said. When the car stalled because the parking brake was engaged, the victims approached the Honda, apparently to ask for Ms. Kitsuwan's purse and to tell Mr. Williams how to disengage the parking brake to keep him from ruining the car, Detective Muniz said. The Civic was recovered the next day just south of the complex. If convicted of capital murder, each could face life in prison or the death penalty. Arlington police arrested the pair Wednesday morning at the Greyhound bus station in downtown Dallas after the two returned from Memphis, Tenn., where the victim's car was found during the weekend.
Investigators believe the slaying resulted from a dispute between the two.
Family members have said the turning point may have been that Ms. Thomas was forcing her granddaughter to move out. Police believe Ms. Thomas was knocked unconscious by a blow to the head during an argument at her central Arlington home. Her body was then thrown from a bridge near Lake Benbrook, southwest of Fort Worth, police said. The body was discovered Friday by a road repair crew. Preliminary autopsy results show that Ms. Thomas died from head injuries and drowned.