Dr. James Kauffman, 68, of Linwood, N.J., was found dead Friday morning in his cell at Hudson County jail, according to the Atlantic County Prosecutor's Office.
According to USAToday, Kauffman was being held at the northern New Jersey facility "as a result of credible threats to his life" when he was originally housed in the Atlantic County Jail, the prosecutor's office said.
Officials said an investigation is continuing and declined further comment.
The men also were accused of operating a drug ring supplied with prescription painkillers from Kauffman's medical office in Egg Harbor Township, N.J. In addition, Augello, 61, was charged with conspiring to murder James Kauffman.
The men had distributed prescription painkillers since 2011, the prosecutor's office alleged. It said the partnership ended in June when investigators arrested James Kauffman on weapons charges after raiding his home and office.
Six other people also face charges in connection with the alleged drug sales.
The prosecutor's office alleged James Kauffman wanted his wife dead to avoid a costly divorce and to prevent her from exposing his drug activities.