HUNTSVILLE, Texas (AP) – A man who fatally stabbed a prostitute almost four years ago was executed Tuesday, becoming the ninth person to be put to death this year in Texas.

Alexander Martinez, 28, ordered that no appeals be filed to stop his punishment.

“I have caused so much pain to so many people,” Martinez wrote in a statement he prepared about two hours before his death. “I especially want to apologize to my victim’s family for the life I took.”

Martinez was supposed to be put to death in March, but the date was delayed after his lawyer filed an appeal against his wishes. The Texas Court of Criminal Appeals later dismissed the appeal.

At least two psychiatrists examined Martinez last year and determined he was mentally competent to make the decision.

Martinez was out of prison only three weeks on an attempted murder conviction when he telephoned an escort service that doubled as a prostitution operation.

With a promise she would be paid $300, Helen Oliveros, 45, showed up at the Houston house where Martinez was staying.

Evidence showed he slit the woman’s throat with a knife, had sex with her and took about $150 from her. He later dumped her body in a vacant field.