South Carolina on Wednesday moved a step closer to adding firing squads to the state's execution methods amid a shortage of lethal-injection drugs.

The bill, approved by a 66-43 vote, will require condemned inmates to choose either being shot or electrocuted if lethal injection drugs aren't available. The state is one of only nine to still use the electric chair and will become only the fourth to allow a firing squad.

South Carolina last executed a death row inmate 10 years ago Thursday.

The Senate already had approved the bill in March, by a vote of 32-11. The House only made minor technical changes to that version, meaning that after a routine final vote in the House and a signoff by the Senate, it will go to Republican Gov. Henry McMaster, who has said he will sign it.

There are several prisoners in line to be executed. Corrections officials said three of South Carolina's 37 death row inmates are out of appeals. But lawsuits against the new death penalty rules are also likely.

"Three living, breathing human beings with a heartbeat that this bill is aimed at killing," said Democratic Rep. Justin Bamberg, rhythmically thumping the microphone in front of him. "If you push the green button at the end of the day and vote to pass this bill out of this body, you may as well be throwing the switch yourself."

South Carolina first began using the electric chair in 1912 after taking over the death penalty from individual counties, which usually hanged prisoners. The other three states that allow a firing squad are Mississippi, Oklahoma and Utah, according to the Death Penalty Information Center.

Three inmates, all in Utah, have been killed by firing squad since the U.S. reinstated the death penalty in 1977. Nineteen inmates have died in the electric chair this century.

South Carolina can’t put anyone to death now because its supply of lethal-injection drugs expired and it has not been able to buy any more. Currently, inmates can choose between the electric chair and lethal injection. Since the drugs are not available, they choose injection.

The bill retains lethal injection as the primary method of execution if the state has the drugs, but requires prison officials to use the electric chair or firing squad if it doesn't.

"Those families of victims to these capital crimes are unable to get any closure because we are caught in this limbo stage where every potential appeal has been exhausted and the legally imposed sentences cannot be carried out," said Republican Rep. Weston Newton.

The lack of drugs, and decisions by prosecutors to seek guilty pleas with guaranteed life sentences over death penalty trials, have cut the state's death row population nearly in half — from 60 to 37 inmates — since the last execution was carried out in 2011. From 2000 to 2010, the state averaged just under two executions a year.

The reduction also has come from natural deaths, and prisoners winning appeals and being resentenced to life without parole. Prosecutors have sent just three new inmates to death row in the past decade.

Democrats in the House offered several amendments, including not applying the new execution rules to current death row inmates; livestreaming executions on the internet; outlawing the death penalty outright; and requiring lawmakers to watch executions. All failed.

Seven Republicans voted against the bill, while one Democrat voted for it.

Opponents of the bill brought up George Stinney, the youngest person executed in the U.S. in the 20th century. He was 14 when he was sent to South Carolina’s electric chair after a one-day trial in 1944 for killing two white girls. A judge threw out the black teen’s conviction in 2014. Newspaper stories reported that witnesses said the straps to keep him in the electric chair didn’t fit around his small frame.

"So not only did South Carolina give the electric chair to the youngest person ever in America, but the boy was innocent," Bamberg said.

Other opponents noted that fellow Southern state Virginia outlawed the death penalty earlier this year. They also pointed out that the three executions carried out so far this year in the U.S. are the fewest since 2008, when the U.S. Supreme Court was reviewing lethal injection.

Newton said the bill wasn't the place to debate the morality of executions.

"This bill doesn’t deal with the merits or the propriety of whether we should have a death penalty in South Carolina," Newton said.