James Lewis, who was convicted of extortion for promising to stop the 1982 Tylenol poisonings for $1 million -- but denied he was behind the seven deaths, has been found dead, police said Monday.

The Massachusetts man served time for sending Johnson & Johnson a letter in 1982 vowing he'd stop the killings that set off panic. The body of the 76-year-old was found Sunday in Cambridge, according to police, who said the death did not appear suspicious.

The unsolved Chicago-area deaths occurred after the over-the-counter Extra-Strength Tylenol capsules were laced with potassium cyanide.

The fears set off by the killings led to major changes in the way medicine was packaged in the US, with tamper-proof safety seals becoming the norm. The poisonings inspired a troubling string of copycats and prompted one of the largest product recalls in history.

Johnson & Johnson, parent of the drug maker, McNeil, was credited for its aggressiveness in recalling the product and its openness in dealing with the killings, and the product quickly bounced back in sales. It remains a popular analgesic.

No one has been charged in the deaths, but Lewis was under periodic police attention.

The Chicago Tribune reported last year that some investigators were still pushing for Lewis to be prosecuted, and that Lewis said he's been treated unfairly and continued to deny involvement.

In 2009, FBI agents searched Lewis's Massachusetts home. Investigators seized a computer from Lewis and collected a sample of his DNA.

The FBI's Boston field office declined to comment Monday on Lewis's death.