I guess I get the 3rd competing story for how it most likely happened..
A man poisoned his cronically ill wife and placed more poisoned pills on store shelves to produce the doubt he didn't murder his wife.
Who actually did the poisoning was not proven due to the number of cases.
"As the tampered-with bottles came from different factories, and the seven deaths had all occurred in the Chicago area, the possibility of sabotage during production was ruled out. Instead, the culprit was believed to have acquired bottles of Tylenol from various supermarkets and drug stores over a period of several weeks, added the cyanide to the capsules, then returned to the stores to place the bottles back on the shelves. In addition to the five bottles that led to the victims' deaths, three other tampered-with bottles were discovered."
Source Wikipedia. http://en.wikipedia.org/wiki/C...