The final execution for the murders of Jennifer Ertman and Elizabeth Pena 17 years ago is set for Tuesday evening in Huntsville.

Peter Cantu, 35, is set to die for his role as the ringleader of the gang that raped, beat and strangled 16-year-old Pena and 14-year-old Ertman in 1993.

Two other men have already been executed and three others remain in prison. Andy Kahan, Houston Police Victim Services Director, said this case has been shocking and precedent-setting from the beginning.

"I've been involved in criminal justice over 26 years and still to this day, it's one of the worst crimes I have ever experienced and I think anyone involved would echo that sentiment," he said.

The families of the victims have forged systematic changes by advocating for victims be to able to attend executions and victim statements to be read in court.

Kahan said he stays in touch with the victims' families. He said they plan to attend the execution.