A condemned Arizona inmate gasped and snorted for more than an hour and a half during his execution Wednesday before he died in an episode sure to add to the scrutiny surrounding the death penalty in the U.S.

Arizona Attorney General Tom Horne’s office said Joseph Rudolph Wood was pronounced dead at 3:49 p.m., one hour and 57 minutes after the execution started.

Wood’s lawyers had filed an emergency appeal with the U.S. Supreme Court while the execution was underway, demanding that it be stopped. The appeal said the convicted killer was “gasping and snorting for more than an hour.”

Word that Justice Anthony Kennedy denied the appeal came about a half hour after Wood’s death.

Wood, 55, gasped more than 600 times before he died. Defense lawyer Dale Baich said the execution should have taken 10 minutes.

Wood was sentenced to death in 1991 for the August 1989 shooting deaths of his estranged girlfriend, Debra Dietz, and her father, Eugene Dietz. Wood and Dietz had a tumultuous relationship during which he repeatedly assaulted her. Dietz tried to end their relationship and got an order of protection against Wood.

Wood went to an auto repair shop in Tucson, where he killed Dietz’s father. He then turned his attention toward Debra Dietz, who was trying to telephone for help. She pleaded with him to spare her life. An employee heard Wood say, “I told you I was going to do it, I have to kill you.” He then called her an expletive and fired two shots in her chest.

Family members of the victims said they had no problems with the way the execution was carried out.

“This man conducted a horrific murder and you guys are going, let’s worry about the drugs,” said Richard Brown, Debra Dietz’s brother-in-law, who witnessed the killings. “Why didn’t they give him a bullet, why didn’t we give him Drano?”

Wood looked at the family members as he delivered his final words, saying he was thankful for Jesus Christ as his savior. At one point, he smiled at them, which angered the family.

“I take comfort knowing today my pain stops, and I said a prayer that on this or any other day you may find peace in all of your hearts and may God forgive you all,” Wood said.

The case has highlighted scrutiny surrounding lethal injections after two controversial executions, including that of an Ohio inmate in January who snorted and gasped during the 26 minutes it took him to die. In Oklahoma, an inmate died of a heart attack minutes after prison officials halted his execution because the drugs weren’t being administered properly.

Arizona uses the same drugs — the sedative midazolam and painkiller hydromorphone — that were used in the Ohio execution. A different drug combination was used in the Oklahoma case.

States have refused to reveal details such as which pharmacies are supplying lethal injection drugs and who is administering them, because of concerns over harassment.

Woods filed several appeals that were denied by the U.S. Supreme Court.

Wood’s execution was Arizona’s third since October and the state’s 36th since 1992.