Lawmakers demanded answers Saturday after wealthy financier and accused sex trafficker Jeffrey Epstein was found dead by apparent suicide, with a number calling for an immediate investigation and justice for his alleged victims.

“The Department of Justice failed, and today Jeffrey Epstein’s co-conspirators think they might have just gotten one last sweetheart deal,” Sen. Ben Sasse, R-Neb., wrote in a fiery letter to Attorney General William Barr on Saturday.

In the letter, a furious-sounding Sasse blasted the Justice Department for the circumstances that allowed Epstein to die by apparent suicide at a federal prison in Manhattan just a little over two weeks after he was found injured and in a fetal position in his cell. He was semiconscious with marks on his neck at the time.

He was not on suicide watch at the time of his death, multiple people familiar with the investigation told NBC News.

“Every single person in the Justice Department — from your Main Justice headquarters staff all the way to the night-shift jailer — knew that this man was a suicide risk, and that his dark secrets couldn’t be allowed to die with him," Sasse wrote. "Given Epstein’s previous attempted suicide, he should have been locked in a padded room under unbroken, 24/7, constant surveillance. Obviously, heads must roll.”

Epstein's death comes a day after a trove of court documents was unsealed providing new details about his alleged crimes. Epstein was arrested July 6 in Teterboro, New Jersey, and was charged with one count of sex trafficking conspiracy and one count of sex trafficking.

Unanswered questions — like how an inmate previously reported to have been on suicide watch was able to kill himself in federal custody — and concern for his alleged victims united lawmakers on both the left and the right Saturday.

Asked about Epstein during a campaign stop at the Iowa State Fair on Saturday, Sen. Elizabeth Warren, D-Mass., said, "The system broke down here."

"He should have been held for trial, and his victim should have had a chance to testify against him. There should have been a public airing of what happened, who helped him, who was involved in it and now all of that's been cut off," the 2020 Democratic hopeful told reporters.

"We need answers. Lots of them," Rep. Alexandria Ocasio-Cortez, D-N.Y., tweeted.

We need answers. Lots of them.https://t.co/4DMckiZnVB — Alexandria Ocasio-Cortez (@AOC) August 10, 2019

Rep. Matt Gaetz, R-Fla., tweeted to agree with Ocasio-Cortez, before taking a political jab at House Democrats for their oversight investigations, including probes of President Donald Trump.

The FBI is investigating Epstein's death in light of the high-profile nature of the case, according to a statement from the federal Bureau of Prisons and a senior law enforcement official familiar with the matter. The FBI does not traditionally investigate suicides at BOP facilities, but Barr said he was "appalled" and that "Mr. Epstein’s death raises serious questions that must be answered."

Barr added that he has ordered the Justice Department's internal watchdog, the Office of the Inspector General, to conduct its own probe.

Rep. Jerry Nadler, D-N.Y., called the apparent suicide "deeply disturbing," saying on Twitter that he was "pleased" that the FBI and the inspector general were investigating.

"There are many questions that need to be answered in this case," Nadler, the chairman of the House Judiciary Committee, said.

While the senior law enforcement official familiar with the matter said there was nothing to suggest foul play at this point, at least one lawmaker publicly expressed doubt.

Rep. Al Green, D-Texas, said suicide was “an impossibility.”

The suicide of Mr. Epstein is an impossibilty. When an impossiblty occurs involving powerful people and possible criminality there must be an investigation to end speculation. Because the public has a right to know, I’m calling for a congressional investigation. #JefferyEpstein — Congressman Al Green (@RepAlGreen) August 10, 2019

“Because the public has a right to know, I’m calling for a congressional investigation,” he wrote in a tweet.

Later, the president himself retweeted a conspiracy theory also casting doubt on the circumstances of Epstein's death, in which a supporter falsely said Epstein had been on suicide watch at the time, and claimed without evidence that President Bill Clinton was likely connected to the apparent suicide.

"Died of SUICIDE on 24/7 SUICIDE WATCH ? Yeah right! How does that happen," wrote Terrence K. Williams, a conservative commentator and comedian, in the message retweeted by Trump. "#JefferyEpstein had information on Bill Clinton & now he’s dead. I see #TrumpBodyCount trending but we know who did this!"

Others voiced new frustration over the outcome of Epstein's prosecution on similar charges over a decade ago in Florida. Epstein ultimately pleaded guilty in 2008 to state charges of procuring a person under 18 for prostitution and felony solicitation of prostitution. He served 13 months, most of it on work release in a private wing of a county jail.

Former Labor Secretary Alex Acosta oversaw the case as U.S. attorney, resigning his post in the Trump administration earlier this year amid renewed scandal over what critics have called a "sweetheart" plea agreement.

"That whole sorry episode of a lack of prosecution was just absolutely disgusting," Washington Gov. Jay Inslee, a Democratic presidential candidate, said. "And Donald Trump's associated with that because he picked the guy that was responsible for that."

Rep. Lois Frankel, D-Fla., and Rep. Jackie Speier, D-Calif., called on the House Oversight Committee to open a probe into Epstein's 2008 deal.

His apparent suicide "does not end the need for justice for his victims or the right of the public to know why a prolific child molester got a slap on the wrist instead of a long prison sentence," Frankel wrote on Twitter.

"Jeffrey Epstein was a serial child molester who evaded accountability because he was rich, powerful, and well-connected. His suicide doesn’t change that. We need answers as to how this could have happened. Most importantly, we need justice for his victims," Speier said in a statement, adding, "Congress has a duty to ensure all those who played a role in this travesty of justice answer to those crimes."

Rep. Frederica Wilson, D-Fla., said on Twitter she was "saddened" that Epstein's alleged victims "have once again been denied their day in court."

Epstein was being held on federal sex trafficking charges after being arrested last month. Federal prosecutors alleged in July that he sought out minors, some as young as 14, from at least 2002 through 2005 and paid them hundreds of dollars in cash for sex at either his Manhattan townhouse or his estate in Palm Beach, Florida. He pleaded not guilty to the charges and was denied bail.

If he had been found guilty, Epstein would have faced up to 45 years in prison.