Schad was 71, and was the oldest person on the state's death row. Grove was 74 when he was killed, shortly after he left his home to travel to Washington state to visit a relative.
The Arizona Republic reported Schad was joking as medical staff inserted catheters in preparation for injection with pentobarbital.
"Well, after 34 years, I'm free to fly away home," he said. "Thank you, warden. Those are my last words."
The lethal injection was administered at 10:03 a.m. MDT and Schad was pronounced dead 9 minutes later.
Schad was convicted in 1979 but the conviction was overturned. He was tried again, convicted, and sentenced to death in 1995.
The Ninth U.S. Circuit Court of Appeals stayed his March execution over questions about whether Schad had received effective legal representation. The U.S. Supreme Court upheld the stay because Schad's attorney did not offer mental illness as a reason not to execute him.
An appeals court subsequently resolved those questions in June, clearing the way for a new execution date, and the Arizona Supreme Court last month ordered the Oct. 9 execution date for Schad.