DALLAS (CBSDFW.COM) – Crime Stoppers has added $20,000 to a reward for information that leads to the arrest and indictment of the person who shot and killed a man while he waited in his car for his mother to get off work last month.

Robert Salas, 28, was waiting in the parking lot of a Marshalls department store at about 11:30 p.m. on May 18. Family members say it’s what he always did –– he would wait in his car at 3434 W. Illinois Ave. to make sure his mother got home safely.

When Rosie Salas got off work and walked up to her son’s car, she found Robert shot to death inside.

Crime Stoppers initially offered $5,000 for any information about the crime, and on Tuesday upped that to $25,000. A Dallas Police Department release said two anonymous donors contributed $10,000 each toward the reward.

Anyone with information about the crime can submit an anonymous tip by calling Crime Stoppers at 214.373.8477 or Dallas’s homicide division at 214.671.3661.