Jack was born into the powerful Napier family, the leaders of the most powerful crime syndicate in the city of Bludhaven known as the Royal Flush Gang. He was their first born son and was thus named Jack and raised to one day take over the gang. That included rigorous classical education as well as intensive combat training. Since birth there was always something off about him. Showing signs of mental and emotional instability. He oddly seemed to run in cycles. Sometimes being just a harmful trickster, and others extremely violent. It did not help thath is father was overbearing and abusive, and despite her efforts to care for him his mother could never really reach him. She tried to secretly hire psychologists to figure out what was wrong with her son after he murdered his elderly governess at the age of six by pushing her down a flight of stairs. The doctor was Smuel Aerons who had an immedate distrust of the boy, and realized the evil that inherently lied within him. Samuel Aerons left in a panic, but disappeared shortly thereafter. His mother Donna was concerned, but his father wanted to hide his son's issues, and refused to send him away as he was his first born son and did not want him to become a disgace to the family. He put his son throuh rigorous mental conditioning to try and fix him, and Jack apparently was eventually put under control.
In his teenage years Jack developed a knack for art and chemistry, as well as the study of philosophy, particularly nihilism. He was sick in his head ever since his childhood, but worked to develop a facade to cover it up. When he turned seventeen he began to get involved in his father's affairs and went on a raid job with some of his father's men. A raid that got messed up, and he himself barely escaped. When he returned his father was infuriated and began to beat him, calling him a disgrace to the family. Eventually Jack pulled out a knife he kept in his jacket and stabbed his father to death in his office. Afterwards he ran away from Bludhaven and went into hiding in its sister city of Gotham, realizing that the punishment for what he did would be severe.
He managed to get transport to Gotham City, where he began work as a petty criminal in the Narrows, one of the worst parts of the town. He took up the alias of Joe Chill in order to sever connections with his family. He hoped to build his own criminal empire, an to prove to himself that he did not need his family to hand him everything on a silver spoon and do whatever he wanted. He eventually joined a gang of hoods. Becoming something of friends (or at least as close as he could be) with another member of his gang named Robert Hawkins (nicknamed Bob). In the early days of his time there Jack and Bob were out and saw the Wayne family walking from a movie theatre. Jack recognized them as being wealthy socialites and convinced Joe that they could mug them to get a nice amount of cash. Jack and Bob followed them into an alleyway where he saw Bruce laughing and having a great time with his parents. Then the mugging began with Bob demanding their valuables. Thomas tried reasoning with them, but the situation escalated to violence when Bob tried to grab a pearl necklace from Martha Wayne's neck. Thomas tried to stop him and during the struggle Jack pulled out his gun and shot him down. Martha began to scream and Jack then shot her as well. Bruce looked around the chaos in panic and Jack then approached him with the gun. Walking into a faint light showing Bruce the demented grin he had on his face. He cocked the gun for the kill but Bob grabbed his arm to lower the gun and told him that they should run. Jack then began to walk away while putting his gun into his jacket and left Bruce with the words, "See you around kid."
Eventually Jack also met a reclusive ex-assassin named David Cain, and managed to complete martial arts training under him and in time became a notorious mob assassin known as the Red Hood, complete wtih a costume. He eventually joined the ranks of the Falcone Crime Organization, as for a long time he was a favorite assassin of theirs. And eventually became the leader of a vicious gang of enforcers that included Chill and eventually another recruit named Willis Todd. Gaining their staunch leadership, the group having a notorious reputation through out Gotham. He fought Batman several times in his early appearances in Gotham.
He was eventually sent to assassinate Sicilian crime lord Franco Bertinelli by Falcone and with his enforcers broke into his home where they had a firefight with his enforcers. Red Hood eventually found Franco and stabbed him to death in a fit of madness and dropped the knife on the ground as he looked at what happened. It was then that his child son Pino ran to his father's side and grabbed Hood's knife and stabbed him in the leg. Hood threw him to the ground and picked up a crowbar one of Franco's men had used as a weapon and proceeded to bash Pino with it in a state of glee. He did not know that he was spotted by one his men who looked at what was being done in horror. Eventually Red Hood and his men escaped from the scene after Pino was dead.
The thug reported to Falcone what he had seen, and despite knowing of the Hood's violent nature knew that that was taken too far and took it as a sign that he was too unstable and decided to have him killed. But given the loyalty many men had to him he had to make it look like he was gunned down by the police. So he had him lead raid on the Ace Chemical Factory where a firefight between his men and the police began. The police being lead by Arnold Flass, a detective in Falcone's pocket with the orders to make sure the HOod was killed. Eventually Batman arrived and started fighting his men as well. Eventually Batman confronted Red Hood on a catwalk over the chemical vats and a fierce fight ensued. Eventually Batman managed to knock Hood's helmet off revealing Jack's face to him. The fight continued and eventually Jack managed to sneak out a knife and stab Batman in the side to subdue him. Jack then flashed his evil grin at him, giving Bruce the realization that the Red Hood was in fact the murderer of his parents as it was the same face Jack had given him in the alleyway. His anger gave Batman a second wind and the fight continued and eventually managed to batter Jack enough to subdue him. Jack pleaded for mercy as Batman picked him up. Batman then threw Jack over the railing of the catwalk and into one of the vats in an attempt to exact the revenge he had always wanted.
But the chemical bath did not kill Jack. The vat was emptied into a river outside of the factory where his body fell into. He barely managed to crawl onto a beach where he was found by some of his escaping men.