Horowitz was one of four non-ghoulified Vault 34 dwellers to still live in the vault. He and a few others were trapped when someone detonated a bomb in the swimming pool area. They left an SOS in the terminal outside the reactor room of Vault 34. Rescuing these survivors is one possible choice during the quest Hard Luck Blues.
He is the de facto leader of the small group of survivors. All of them wear Vault 34 jumpsuits. They can be killed without loss of Karma.
If the player rescues Horowitz and the other Vault 34 human survivors, they will eventually find their way to the Aerotech Office Park Suite 300, west-southwest of Vault 34. If you talk to him there, he will tell you that his group is really glad to be freed from the vault and is excited to learn more about the surface world. They also mention that the NCR officer in charge of the office park accepted their group and offered them free food and shelter. You have the option of telling them that you were the one who freed them. If you do so they will express their thanks to you.
pcps3xbox360 After the Vault 34 survivors appear in the Aerotech office park (assuming the player chose to save them), speaking to Horowitz will provide a dialogue option for a reward: a "Vault Trinket"; however, no item is added to your inventory if this dialogue option is selected, and there is no indication within the game's code as to what this item was intended to be. [verified]
pcps3 Sometimes Horowitz and the rest of the Vault 34 dwellers will not spawn at Aerotech and even if you saved them, attempting to use the console commandplayer.moveto Ref ID may also not work. You will be teleported to the location within Aerotech (Aerotech Suite 300), but it will be empty. The only way to fix this is to target each non-player character with the console, enter prid Ref ID and activate for each of them individually. [verified]