The Tylenol murders occurred in the autumn of 1982, when seven people in the Chicago, Illinois, area in the United States died after ingesting Extra Strength Tylenol medicine capsules which had been laced with cyanide poison. This incident was the first known case of death caused by deliberate product tampering. The perpetrator has never been caught, but the incident led to reforms in the packaging of over-the-counter substance and federal anti-tampering laws.
I recall reading about this case where it was claimed the murderer was caught. I believe it was a woman who poisoned her husband for his life insurance but tried to cover the crime by randomly poisoning others via placing cyanide in Tylenol. You might want to Google this.