Huntsville, Tex. ? A man convicted of killing a Dallas police officer in 1988 was executed Wednesday despite protests that putting him to death violated international law.

Speaking English and Spanish, Javier Suarez Medina apologized for the crime, asked forgiveness from the relatives of the slain police officer and thanked the people of Mexico for their support in his case.

“I’d like to apologize to the Cadena family for whatever hurt and suffering I’ve caused them,” he said in a final statement that lasted several minutes. “I sincerely ask in your heart to forgive me.”

As the lethal injection was administered, Suarez began singing the hymn “Amazing Grace.” He was pronounced dead nine minutes later.

The mother and son of the officer were among the execution witnesses. Afterward, Lawrence Cadena Jr. thanked local and federal authorities “who helped push this through the system.”

Court appeals and protests against the execution argued Suarez was not told he could contact the Mexican consulate for help after his arrest, violating the 1963 Vienna Convention of Consular Relations, which the United States has signed.

Dallas authorities have said Suarez, 33, gave conflicting information when asked about his birthplace, identifying both Mexico and Texas. He spent most of his life in the United States and spoke English.

The U.S. Supreme Court, without comment, turned down an appeal about 90 minutes before the scheduled execution. Gov. Rick Perry then denied Suarez a 30-day reprieve.

Suarez was convicted of gunning down Dallas police Officer Lawrence Cadena, 43, during an undercover drug sting. He was 19 at the time.

Mexican President Vicente Fox late Wednesday canceled a planned trip to Texas after the execution.

A Fox spokesman said the trip, which had been scheduled for Aug. 26-28, is seen as “inappropriate under these lamentable circumstances.”