Prosecutors alleged Epstein and his associates had paid dozens of underage girls, some as young as 14, to engage in sex acts. He was facing up to 45 years in jail.
Now he will never be brought to justice.
Attorney-General William Barr heads the US Justice Department, which was ultimately responsible for Epstein, as he was being held in a federal prison.
Barr is demanding answers.
"I was appalled to learn that Jeffrey Epstein was found dead early this morning from an apparent suicide while in federal custody," he said today.
"Epstein's death raises serious questions that must be answered. In addition to the FBI's investigation, I have consulted with the Inspector General who is opening an investigation into the circumstances of Epstein's death."
Both investigations will examine the baffling decision to take Epstein off suicide watch, despite a suspected suicide attempt less than three weeks ago.
Epstein was found unconscious in his cell with bruises on his neck on July 23. Officials were unsure whether the injuries were the result of self-harm or an assault by a fellow inmate.
As you would expect, all federal prisons in the United States have measures in place to protect inmates who are at risk of taking their own lives.
After the incident on July 23, Epstein was placed on suicide watch.
What does that mean, exactly? According to The New York Times, such inmates are "generally placed in a special observation cell, surrounded with windows, with a bolted down bed and no bedclothes". Someone is assigned to monitor them at all hours.
CNN reports Epstein underwent daily psychological assessments during that time. At the end of July, psychologists from the Bureau of Prisons made the call to take him off.
Typically, that decision would need to be approved by both the facility's chief psychologist and the warden.
Keeping someone on watch and monitoring them constantly does sap prison resources, often forcing staff to work overtime, so typically the arrangement only lasts a few days.
Nevertheless, legal and prison experts slammed officials today.
"For them to pull him off suicide watch is shocking," former warden Cameron Lindsay told NBC News.
"For someone this high profile, with these allegations and this many victims, who has had a suicide attempt in the last few weeks, you can take absolutely no chances."
After he was taken off 24-hour monitoring, Epstein was held in the Manhattan Correctional Centre's "Special Housing Unit", a section of the prison isolated from the general population.
A former MCC inmate, who spent four months in the SHU, told the New York Post it should have been impossible for Epstein to take his own life there.
"There's no way that man could have killed himself. I've done too much time in those units. It's an impossibility," the anonymous inmate said.
"And there's a cop at the door about every nine minutes, whether you're on suicide watch or not."
Officials will review prison footage to see whether guards were checking on Epstein as frequently as they were supposed to.
Another consideration is that the MCC, which holds more than 700 inmates, has a number of cells with cameras. Was Epstein put in one of them? If so, why was no one monitoring it? And if not, why not?
The MCC has notoriously high security. It has previously held drug lord Joaquin "El Chapo" Guzman, mob boss John Gotti and the World Trade Centre bombers.
"This happened in one of the most secure and most important federal lockups in the country. Not some county jail or state prison," said George Conway, a prominent lawyer and the husband of White House adviser Kellyanne Conway.
"With the most high profile pre-trial detainee in the country. Who had tried to kill himself once just days ago. I mean, stuff happens, but this is beyond astounding."
Then there are the inevitable conspiracy theories. Epstein's sex trafficking ring reportedly involved a number of powerful people. So far, we don't know who most of them are, but today authorities promised they would keep investigating.
"I am not into conspiracy theories. But Epstein had destructive information on an extraordinary number of extraordinarily powerful people. It is not easy to commit suicide in prison. Especially after being placed on suicide watch. Especially after already allegedly trying," said lawyer and public defender Scott Hechinger.
In a letter to the Attorney-General, Republican Senator Ben Sasse warned Epstein's "co-conspirators" would react with relief to his death.
"The Department of Justice failed, and today Jeffrey Epstein's co-conspirators think they might have just gotten one last sweetheart deal," 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.
"It should have been abundantly clear that Epstein would go to any lengths to avoid being held accountable for his crimes ... being responsible for Epstein's custody and prosecution, the Department of Justice should not have allowed this to happen."
President Donald Trump, who has always had a taste for conspiracy theories, took the extraordinary step of retweeting people suggesting the Clintons were involved.
The day before Epstein's death, unsealed court documents showed former president Bill Clinton had travelled on the billionaire's plane.
Flight logs also show Trump made one trip on the plane.
The President has frequently spread conspiracy theories about his political opponents.
Trump was a leading proponent of the theory that Barack Obama was not an American citizen. During the 2016 election campaign, he suggested Republican opponent Ted Cruz's father had been involved in the assassination of John F. Kennedy, and fomented rumours Hillary Clinton was suffering from a debilitating illness.
There is no evidence to support any of those claims.
While Trump was spreading conspiracy theories, the office investigating Epstein's underage sex ring released a statement saying its work would continue.
"Today's events are disturbing, and we are deeply aware of their potential to present yet another hurdle to giving Epstein's many victims their day in court," Manhattan US Attorney Geoffrey Berman said.
"To those brave young women who have already come forward and to the many others who have yet to do so, let me reiterate that we remain committed to standing for you, and our investigation of the conduct charged in the indictment, which included a conspiracy count, remains ongoing."
Berman urged any other victims, or anyone with information related to the case, to contact the FBI.
WHERE TO GET HELP:
If you are worried about your or someone else's mental health, the best place to get help is your GP or local mental health provider. However, if you or someone else is in danger or endangering others, call 111.
If you need to talk to someone, the following free helplines operate 24/7:
DEPRESSION HELPLINE: 0800 111 757
LIFELINE: 0800 543 354
NEED TO TALK? Call or text 1737
SAMARITANS: 0800 726 666
YOUTHLINE: 0800 376 633 or text 234
There are lots of places to get support. For others, click here.
