Cyanide Poisoning?
@Forest_Wood For,a start, here ya go.
"Cyanide poisoning is poisoning that results from exposure to any of a number of forms of cyanide.[4] Early symptoms include headache, dizziness, fast heart rate, shortness of breath, and vomiting.[2] This phase may then be followed by seizures, slow heart rate, low blood pressure, loss of consciousness, and cardiac arrest.[2] Onset of symptoms usually occurs within a few minutes.[2][3]....
"Acute exposure
"If hydrogen cyanide is inhaled, it can cause a coma with seizures, apnea, and cardiac arrest, with death following in a matter of seconds. At lower doses, loss of consciousness may be preceded by general weakness, dizziness, headaches, vertigo, confusion, and perceived difficulty in breathing. At the first stages of unconsciousness, breathing is often sufficient or even rapid, although the state of the person progresses towards a deep coma, sometimes accompanied by pulmonary edema, and finally cardiac arrest."
A lot more info at link for your reading pleasure.
Personally not gonna Google --- where to buy cyanide.