(CNN) -- A flurry of last-minute legal maneuvers Tuesday spared, for now, the life of John Ferguson, a Florida death row inmate who suffers from mental illness and at one point called himself the 'prince of God.'
Ferguson, a diagnosed schizophrenic convicted of killing eight people, was scheduled to get the lethal injection Tuesday at 6 p.m. ET at a Florida State Prison.
But an appeals court in Atlanta granted an emergency stay of execution Tuesday night.
Florida officials then asked the Supreme Court to allow the lethal injection to proceed. Just before midnight the high court denied Florida's request, keeping in place the stay of execution, according to court documents.
Some had questioned why authorities would kill a man who suffered from mental illness.
Laurel Bellows, the president of the American Bar Association, released a statement earlier Tuesday saying she was concerned about how thoroughly Ferguson's competency was evaluated.
"The American Bar Association is alarmed that Florida is poised to execute John Ferguson, a man diagnosed as severely mentally ill for more than 40 years, before the constitutionality of his execution is fully evaluated."
Chris Handman, one of Ferguson's attorneys, told CNN. "We think the court should intervene to stop that execution from going forward."
Handman said a court had earlier found that Ferguson was mentally ill and had delusions that caused him to think he is the "Prince of God."
Ferguson is on death row for the murders of eight people in Hialeah and Carol City, Florida, in the late 1970s.
Lawyers from both sides will now be allowed to file motions on the case and it was unclear when a hearing would be scheduled to decide Ferguson's fate.
As the legal wrangling went on Tuesday, Florida prison officials poceeded as if the execution was going to take place, putting Ferguson in isolation and giving him his last meal.
The convicted killer, prison officials said, ate a "last meal" of a country-fried chicken sandwich and sweet tea.
CNN's Bill Mears, Nick Valencia, Joe Sutton and Jason Hanna contributed to this report.