Hooded Justice was the first "real world" vigilante, the inspiration for the first Nite Owl (Hollis Mason) and all the vigilantes to follow; he was a member of the the original justice society, the Minutemen, in 1939. His name and background remain unknown and open to conjecture.
"HJ," as he was affectionately known, might have been circus strong man, Rolf Muller, according to Hollis Mason in his book, Under the Hood. He literally burst on the scene by brutally attacking street thugs in 1938. While he did "keep up appearances" by posing as the first Silk Spectre's (Sally Jupiter) love interest, he was undoubtedly homosexual--always in the "company of boys." To that end, the Comedian (Edward Blake) exposed Hooded Justice's sadistic sexual perversion that basically drove him to vigilantism under the deluded rationalization of righteousness.
Hollis Mason also claimed HJ openly approved of the Third Reich.
During the McCarthy era, Hooded Justice disappeared after he refused to testify in Senate hearings and refused to reveal his true identity. According to Ozymandias (Adrian Veidt)--during his subsequent investigation of his disappearance--HJ was, in fact, murdered by the Comedian--perhaps as a government plot against Communists and other undesirables and/or in retaliation for the beating Comedian took at HJ's hands when he sexually assaulted Silk Spectre.