"Those who are responsible for what happened to Bob Levinson, including those in the U.S. government who for many years repeatedly left him behind, will ultimately receive justice for what they have done", their statement said.
The statement said Levinson's family received the news from U.S. officials but did not know how or when he died, only that his death preceded the coronavirus outbreak that has ravaged Iran.
"It is impossible to describe our pain", the statement said. "Our family will spend the rest of our lives without the most awesome man, a new reality that is inconceivable to us".
Levinson, who was Jewish, is survived by his wife, Christine, seven children, and numerous grandchildren.
"To be clear, the Iranian regime is fully responsible for Bob Levinson's disappearance and his death", said Menendez, the top Democrat on the Senate Foreign Relations Committee.
Shortly afterward, Levinson disappeared, but Iran repeatedly denied capturing him or knowing of his whereabouts. "They will only know him through the stories we tell them".
The family added they did not know if or when his body would be returned. The outlet noted that Levinson was "the longest-held hostage in USA history".
Fox News reported that "Levinson was 58 years old when he traveled to Kish Island, Iran, in 2007 working as a private investigator as part of an unauthorized Central Intelligence Agency mission allegedly probing cigarette smuggling". For years, United States officials would only say that Levinson was working independently on a private investigation.
Information from The Associated Press was used in this report. They were sent three emails from his captors, who didn't identify themselves and demanded millions of dollars and the release of several prisoners in exchange for Levinson's release.
Secretary of State Mike Pompeo, in an attempt to get Iran to release several USA hostages, offered a $25 million reward for information leading to Levinson's recovery and return but to no avail.
Tehran denied knowledge of Levinson's whereabouts until November a year ago when it acknowledged that there was an ongoing case involving him before its revolutionary court. Relatives took that as the first real acknowledgement that Robert Levinson was in custody and being moved through the Iranian justice system. Though the development gave the family a burst of hope, Iran clarified that the "open case" was an investigation into his disappearance.