WILMINGTON - A federal judge on Wednesday halted the execution of convicted killer Shannon Johnson, saying he wants to hear oral arguments over claims that Johnson is mentally incompetent and should not be executed.

The decision by U.S. Chief District Judge Gregory Sleet stunned prosecutors, who noted that the incompetency claims were made by federal public defenders who were not authorized by Johnson to intervene in the case.

Johnson was scheduled to be executed Friday. Prosecutors immediately began preparing an appeal of Sleet's decision, which was docketed with the U.S. Court of Appeals for the Third Circuit in Philadelphia late Wednesday afternoon. It was unclear whether the appeals court would act before Sleet heard oral arguments, set for Monday, but the appeals court directed the federal public defenders to respond to the state's motion to vacate the stay of execution by 8a.m. Thursday.

Prosecutors said in their appeal that Sleet "paid no recognition" to the appropriate standard for staying an execution and had abused his discretion.

Johnson has waived his right to future appeals and indicated that he wants to be executed as soon as possible. His state-appointed attorney also opposed Wednesday's ruling.

"It is Mr. Johnson's view that he has been afforded all constitutional due process," Jennifer-Kate Aaronson told the judge.

Johnson was sentenced to death for the 2006 murder of Cameron Hamlin, 25, who was shot after Johnson found him sitting in a car with his ex-girlfriend near downtown Wilmington. Johnson later shot the former girlfriend, but she survived.

After the state Supreme Court upheld his conviction and death sentence in 2009, Johnson said he did not want to pursue further appeals.

Following a six-day competency hearing last year, Superior Court Judge M. Jane Brady declared in February that Johnson was mentally competent to waive his right to further appeals, and that he understood the legal consequences of that decision. Last month, she scheduled the execution date after Johnson waived his right to a requirement that an execution be held no sooner than 90 days from the sentencing date.

After Johnson sought to waive his further appeals, federal public defenders tried to intervene without his consent, arguing that he was incompetent because he was mentally disabled. Brady refused to allow them to participate in the state court competency hearing, and they defied her order to turn over their files on Johnson to state prosecutors and Johnson's state court attorneys.

Sleet subsequently ordered the federal public defenders to turn over their files to prosecutors and defense attorneys. He also voided their appointments to represent Johnson. Nevertheless, the public defenders filed court papers last week attempting to intervene in the case again, asserting that they were acting on behalf of Johnson's sister, Lakeisha Ford, as his "next friend."