Image from 1975 Senator Frank Church shows off the CIA’s top secret weapon known as the “Heart Attack Gun” when the CIA unveiled the Heart Attack Gun. It was powered by an electric battery and fired a dart of frozen water containing a poisonous toxin that, upon entering the victim’s bloodstream, caused death by “heart attack” without leaving a trace of external causes in the autopsy. And it only left a small entrance wound. It had a range of 100 meters. It was revealed after a US Congress commission on illegal methods used by the CIA. It is unknown where the weapon ended up and if it was used in operations. Yes, it was revealed that it had been tested on animals and prisoners.
The weapon development
The CIA needed a weapon to take care of the targets on their blacklist without living any sort of trace that would bring up suspicions in the media. One of the hot targets was Fidel Castro, the Prime Minister of Cuba from 1959 to 1976. Killing people from a distance was the go-to choice, but every bullet can be traced back. Getting too close to the target would risk the agent being compromised.
This is why the CIA gave the task of creating a new secret weapon to Mary Embree. Embree started working at the CIA as a secretary in the audio surveillance department. With time she got promoted to the technical services department where she was asked specifically to research a new poison that would induce a heart attack on its victim but undetectable in a post-mortem verification. More info