Feb 28 - A 70-year-old man convicted of murdering his estranged wife's parents and brother in 1989 was executed in Texas on Thursday, hours after the U.S. Supreme Court denied a petition seeking a reprieve on grounds he received inadequate defense at his trial.Billie Wayne Coble was pronounced dead at 6:24 p.m. CST (0024 GMT Friday) from lethal injection at the state death chamber in Huntsville, the Texas Department of Criminal Justice said in a statement.His last words, according to the department, were: "That will be five dollars. Take care."It was the third execution this year in the United States and the second in Texas, which has put more inmates to death than any other state since the U.S. Supreme Court reinstated capital punishment in 1976.Coble, a Vietnam War veteran and electrician, was convicted in 1990 of slaying his estranged wife's mother and father, Robert and Zelda Vicha, and her brother, John "Bobby" Vicha, who was a police sergeant. Coble's wife had sought a divorce at the time.Coble ambushed the three victims and shot them at their home in Axtell, a small community 100 miles (160 km) north of the state capital, Austin, authorities said in court papers.He then kidnapped his estranged wife and drove off with her.He was chased by police and, while driving, stabbed her with a knife. He eventually crashed into a parked car and was arrested. His wife survived.