Timeline: What led to Arkansas' double execution

— -- When Arkansas carried out death sentences for two inmates on Monday evening, it was part of the state's controversial plan to execute eight people by the end of the month, when its supply of a drug used in the process of lethal injection reaches its expiration date.

It was the first double execution in the U.S. since 2000, when Texas carried out the death sentences of two convicted killers.

The drug in question is midazolam, a sedative that pharmaceutical companies are no longer providing to states for use in executions, and one part of a three-drug cocktail that the state employs during the lethal injection process.

Here's what led to Arkansas' double execution Monday:

Feb. 27, 2017

Arkansas Gov. Asa Hutchinson sets execution dates for eight death row inmates between April 17 and April 27, 2017, to occur before the April 30 expiration of the state's supply of midazolam.

March 13, 2017

Arkansas acquires an unknown amount of potassium chloride, the third and final drug in its execution protocol that's used to stop the heart, according to the Arkansas Democrat-Gazette.

March 21, 2017

The Arkansas Democrat-Gazette reports a shortage of required citizen witnesses to watch the eight lethal injections.

The state prison director is then prompted to call on Rotary Club members to volunteer, according to the paper.

March 27, 2017

Nine death row inmates, including the eight scheduled for death in April, file lawsuits to halt the executions.

April 6, 2017

The Arkansas Supreme Court rules against halting the lethal injection of two inmates who were scheduled for execution, Stacey Eugene Johnson and Ledell Lee.

The court didn't elaborate on its reason for denying the requests, according to The Associated Press.

April 17, 2017

A U.S. Supreme Court decision effectively blocks the execution of death row inmate Don Davis, a convicted murderer, moments before it was scheduled to occur.

The ruling followed protests that had been growing around the Arkansas Governor's Mansion in Little Rock, where activists and some officials have called for the prisoners' reprieve. Among the officials was Pulaski County Circuit Judge Wendell Griffen, who was later barred from taking on capital punishment cases and referred to a disciplinary panel after he "lay on a cot as though he were a death row inmate on a gurney," according to the AP.

The demonstrations also included several high-profile names, such as Damien Echols of the West Memphis Three, a former death row inmate who was released in 2011, and actor Johnny Depp.

Brian Gallini, the associate dean of the University of Arkansas School of Law, told ABC News at the time of the protests that the attorney general's office was within its legal rights to try and complete the remaining executions but that the issue of scheduling raised many questions about the process, including how the state plans to follow through on them after the drug expires.

"I think the impression of rushing is that there's no plan B," he said. "It's fine to want to bring justice for the victim's families but what is the plan B for doing that? It's still not clear."

Austin Sarat, professor of jurisprudence and political science at Amherst College and the author of "Gruesome Spectacles: Botched Executions and America's Death Penalty," told ABC News then that the state's aggressive plan significantly raises the risk of the state making a mistake in carrying out one or more of the executions.

"When you combine the compressed schedule of executions and the fact that the state hasn't carried one out in so long, it increases the risk for a mistake or a botched execution," Sarat said regarding Arkansas.

The state, for its part, said that after years of delay, death row prisoners should face their prescribed punishments to bring justice to the families of victims of their crimes. “As is oft said, justice delayed is justice denied,” the state attorney general’s office argued in a brief supporting a motion to vacate the stay of execution. “Now, the time has come to see that justice is done.”

April 20, 2017

Just before midnight, the state executes Lee by lethal injection. It's the state's first execution since Eric Randall Nance was executed in 2005.

Newly appointed Supreme Court Justice Neil Gorsuch joined with four conservative colleagues to allow the state's lethal injection process to go forward in Lee's execution.

It was the first time he faced a vote in which he could have spared a man's life, according to the AP.

April 24, 2017

Arkansas carries out death sentences for two more inmates through lethal injection, marking the country’s first double execution in nearly 17 years.

Convicted murders Jack Jones, 52, and Marcel Williams, 46, were executed just hours apart from each other.

Jones was executed at 8:20 p.m. for the rape and murder of a bookkeeper in 1995. Williams was executed about three hours later for the 1994 murder of a young mother.

It was the first time a state has executed two people on the same day since Texas killed two inmates in August of 2000.

ABC News' Karma Allen and J.J. Gallagher contributed to this report.