Updated March 21, 5:55 p.m. – Russell Bucklew's scheduled execution has been called off.

In a 5-4 vote, the U.S. Supreme Court issued a stay Tuesday evening, based on Bucklew's assertion that Missouri's lethal injection protocol would cause bleeding and suffocation due to a medical condition he suffers.

Justice Anthony Kennedy acted as the swing vote, siding with Ruth Bader Ginsburg, Sonya Sotomayor, Elena Kagan, and Stephen Breyer in granting the stay. Justices Clarence Thomas, Samuel Alito, Neil Gorsuch, and Chief Justice John Roberts voted against.

“We’re very relieved… as we got closer to 6-o'clock, I started to get a little nervous and had to wonder if we were going to have to watch something horrific,” said Esmie Tseng of Missourians for Alternatives to the Death Penalty. “I’m not a doctor, but we’ve had medical experts who found that there’s a very high chance that these tumors could rupture, and that the lethal injection drug won’t circulate properly.”

The stay, though, is temporary. The High Court will now consider whether to overturn a lower court ruling that stated Bucklew could not say for sure that lethal injection via pentobarbital would cause choking or bleeding. If the Supreme Court does not overturn that ruling, then Missouri would have clearance to attempt a third execution of Bucklew.

Credit Missouri Dept. of Corrections

The High Court could also direct that Bucklew’s medical claims be reheard in federal district court.

His attorney, Cheryl Pilate, said Wednesday that their appeal included a suggested alternate method of execution – lethal gas.

“As part of our case, we had to allege a feasible, available alternative method of execution,” she said. “Whether or not the state regards that as feasible, or whether the state is prepared to proceed with lethal gas, is an issue up to them – but it is the other method authorized by Missouri statute.”

Bucklew is also hoping that Governor Eric Greitens will spare his life.

“We have made an application for executive clemency,” Pilate said, “but that has not been decided upon.”

No one from Greitens’ office has responded yet to requests for comment.

Regardless of what the U.S. Supreme Court decides, there won’t be a new execution date anytime soon.

“The Missouri Supreme Court will have to set a new date following review of the appeal,” Department of Corrections spokeswoman Karen Pojmann said in an email to St. Louis Public Radio.

Bucklew was minutes away from being executed in 2014 when the Supreme Court issued its first stay.

“For the second time in four years, the Supreme Court has intervened to stop the unconstitutional and barbaric proposed execution by lethal injection of Russell Bucklew," said Cassandra Stubbs, director of the ACLU's Capital Punishment Project. "While the Supreme Court’s decision to stay the execution is a welcome one, it is an indictment of our legal system that Mr. Bucklew came this close to execution. As a result of his unique medical condition, Mr. Bucklew could have choked on his own blood during the execution and experienced excruciating pain. Neither the constitution nor the bounds of human decency permit his execution."

Bucklew, 49, was sentenced to death for the murder of Michael Sanders in Cape Girardeau County.

On March 21, 1996 — exactly 22 years ago Wednesday — he entered a trailer where Sanders lived with Bucklew’s ex-girlfriend, Stephanie Ray. Bucklew shot Sanders in front of Ray, then kidnapped and raped her.

He was later captured after a shootout with state troopers. Bucklew and a state trooper were both wounded while exchanging gunfire.

Lt. Eric Friedrich of the Cape Girardeau County sheriff’s office, who investigated the case against Bucklew 22 years ago, wanted the execution to go forward.

"I think about the pain that he inflicted...on the Sanders family and the pain that he inflicted on Stephanie Pruitt (Ray) and what her life was like thereafter,” Friedrich told Cape Girardeau TV station KVFS.

Follow Marshall on Twitter:@MarshallGReport