Carl Weiss was born in Baton Rouge, Louisiana in 1906. He graduated from Tulane University Medical School and did postgraduate work in Austria.

On September 8, 1935, Weiss shot Huey Long in the Capitol building at Baton Rouge, Louisiana. Weiss's father was head of one of Long's hospitals that was about to open at the time. It is speculated that Weiss, after visiting Germany earlier in 1935, saw parallels between Huey Long and Adolf Hitler and assassinated him for that reason.