The Texas Court of Criminal Appeals has halted the scheduled execution later this month of a man convicted of killing a Houston police officer 28 years ago.

It's the fourth execution stopped by the court over the past month. Different issues were raised in each.

Fifty-eight-year-old Robert Jennings was set for lethal injection Sept. 14 for fatally shooting Elston Howard, a Houston police vice officer, at an adult bookstore in Houston in July 1988.

Jennings' attorneys have questioned whether jury instructions during the punishment phase of his trial were proper.

Jennings was on parole at the time after serving 10 years of a 30-year sentence for robbery.

Witnesses said the officer was arresting a bookstore clerk for showing movies without a license when Jennings walked in and opened fire.