Sen. Ben Sasse of Nebraska sent a letter to Attorney General William Barr Saturday afternoon demanding the Department of Justice investigate Jeffrey Epstein's apparent suicide in jail. Sasse also called for those who allowed Epstein's death to occur under their watch to be fired.

Epstein, who was facing federal sex trafficking charges, died Saturday in an apparent suicide, federal officials said. The federal Bureau of Prisons said in a statement that the FBI was investigating his death.

"The Department of Justice failed, and today Jeffrey Epstein's co-conspirators think they might have just gotten one last sweetheart deal. 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," the Republican senator wrote in his letter to Barr.

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Epstein was found injured in his jail in late July, and was under observation at the time, law enforcement sources told CBS News at the time.

"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," Sasse continued.

Sasse asked Barr confirm he is ordering two investigations: one into the Bureau of Prison's mismanagement of Epstein's incarceration, and one into potential criminal activity surrounding this mismanagement.

Barr has already indicated he will take action to investigate the circumstances surrounding Epstein's death. A person familiar with Barr's thinking told CBS News that Barr was livid about Epstein's death and was determined to get to the bottom of it. In a statement, Barr said he was "appalled" by the death.

"Mr. Epstein's death raises serious questions that must be answered," Barr said. "In addition to the FBI's investigation, I have consulted with the Inspector General who is opening an investigation into the circumstances of Mr. Epstein's death."

Democratic Rep. Jackie Speier also called for an investigation into Epstein's death on Saturday.

"Jeffrey Epstein was a serial child molester who evaded accountability because he was rich, powerful, and well-connected," Speier said in a statement. "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 also called for an investigation by the House Oversight Committee into Epstein's 2008 plea deal. Epstein spent 13 months in a Florida county jail and had to register as a sex offender but faced immunity from federal prosecution. Alexander Acosta, who was the U.S. attorney in Florida's Southern District at the time and oversaw the plea deal, resigned as Labor Secretary in July after facing renewed scrutiny over it.

Court documents were unsealed Friday from a lawsuit filed by a woman who alleged Epstein trafficked her for sex in several locations and on Epstein's private plane. The woman, Virginia Giuffre, named Britain's Prince Andrew, former New Mexico Gov. Bill Richardson and former Sen. George Mitchell among others in the documents. Richardson and Mitchell issued statements Friday denying any involvement with Epstein.