Between September 29th and October 1, 1982, four women, two men and a child died before medical personnel determined the common link to their deaths was Tylenol.
"No one has claimed responsibility, and we won't know the motivation behind the crime until we identify the persons responsible," said Ross Rice, FBI spokesperson
The only known suspect identified in the case is James Lewis, who was convicted and served time for writing this extortion letter to Johnson and Johnson, the maker of Tylenol. But he was never charged with the murders.
The case had gone dormant until five years ago when the FBI and local police departments formed a task force. Three years ago, they searched the apartment Lewis shares with his wife in Boston, confiscating several possible items of evidence.
Retired Chicago detective Dave Ryan worked the extortion case against Lewis and believes he is also the killer.
"The fact that we weren't able to assemble or gather enough evidence to satisfy a court of law or even charge him is one thing, but kind of knowing who did it is another," said Ryan.
Lewis even provided detectives with sketches of how the killer could have put cyanide into the tablets. He's even written a book about it. But he has always denied any involvement in the actual killings.
Meanwhile, investigators continue to pour resources into finding the killer.
"It's a horrific crime and it's gone unsolved," said Rice.
Johnson and Johnson removed 30 million bottles of Tylenol from the shelves in 1982 and offered a $100,000 reward, which still stands. There is no statute of limitations on murder in Illinois.