Updated

Colorado Gov. John Hickenlooper indefinitely delayed the execution of convicted killer Nathan Dunlap on Wednesday and said he was unlikely to allow it as long as he is governor.

Hickenlooper said he had doubts about the fairness of Colorado's death penalty system and about the state's ability to get the lethal drugs required for an execution.

Dunlap, 38, was convicted and sentenced to die in 1996 for the ambush slayings of four people in a Denver-area restaurant. Hickenlooper's action essentially guarantees Dunlap will survive through Jan. 13, 2015, the last day of Hickenlooper's first term. Hickenlooper plans to run for re-election, and the reprieve is sure to be a campaign issue.

Dunlap, whose execution was scheduled for the week of Aug. 18, got only a reprieve, not the clemency he sought. Clemency would have removed the possibility of execution and changed his sentence to life without parole.

Dunlap could conceivably be executed one day if another governor lifts the reprieve.

Hickenlooper's announcement infuriated prosecutors and some of the victims' relatives.

"He took a coward's way out," said Melinda Cromar, whose 19-year-old sister Sylvia Crowell was killed. "I am just so angry."

District Attorney George Brauchler said Hickenlooper had made no decision at all.

"He could have made a decision I disagreed with. He could have made a decision I agreed with. But to not make a decision is an injustice," said Brauchler, the top prosecutor in the district where Dunlap was convicted.

Madeline Cohen, one of Dunlap's attorney's expressed relief.

"I'm very, very glad that the governor has decided not to go forward and has recognized how many problems there are in the system," she said.

Hickenlooper said he listened to all sides and considered the decision carefully.

"We heard a variety of sides and obviously this has weighed heavily on me for well over a year now," he said at a news conference.

Dunlap has acknowledged fatally shooting four employees -- three of them teenagers -- who were cleaning a Chuck E. Cheese restaurant after hours in the Denver suburb of Aurora.

Dunlap, then 19, had recently lost a job there as a cook. On the night of Dec. 14, 1993, he hid in a restaurant bathroom until the restaurant closed, then shot and killed Crowell; Ben Grant, 17; Colleen O'Connor, 17; and Margaret Kohlberg, a 50-year-old mother who was on her first day on the job.

Each was shot in the head. A co-worker Bobby Stephens, then 20, was also shot in the head, but he survived and testified against Dunlap.

One of the victims was down on her knees and begging for her life when Dunlap shot her.

Dunlap lost his last mandatory appeal in February, and his lawyers petitioned Hickenlooper for clemency and also filed other lawsuits challenging the sentence and execution process.

In his reprieve, Hickenlooper said Colorado's capital punishment system is flawed, citing a study that showed the death penalty was sought and imposed inconsistently across the state.

He also said the state doesn't have the drugs in place to carry out an execution by lethal injection, and that many states and nations are repealing the death penalty.

Hickenlooper's reprieve order mostly referred to Dunlap by his state prison number.

"I don't use his name. I haven't with any of these mass killings because I don't think he needs any more notoriety," Hickenlooper said at the news conference.

Dunlap's attorneys say he was remorseful, and they released a video and written statement in which Dunlap apologized.

They also said he had undiagnosed bipolar disorder at the time of the shootings.