Danny, Ish, our protectors.
— A child's view of Danny and Ish.
While Danny is not physically encountered by Joel and Ellie during the events of the game, notes scattered within the man's former settlement provide some guidance to his life there. Given the presence of Clickers in the areas where these notes are discovered, it would seem the events happened a considerable time beforehand.
It is unknown what Danny did for a living prior to outbreak. He likely lived in or around Pittsburgh.
After the outbreak, Danny eventually made his way to the sewers where he discovered a thriving community led by a man named Ish, a former fisherman,  who had formed the community after joining a family consisting of Kyle, Susan and their children.  due to becoming lonely.  The safehouse consisted of a school, makeshift beds, shower stalls, and even rain catchers. 
Ish and Danny became the protectors of the community, salvaging, armor, Assault Rifles and sawed off shotguns from dead soldiers. Joel could find a picture of Danny alongside Ish when exploring the sewers. A child had drawn him next to Ish, calling the two "[their] protectors". 
At an unknown point in time, a door leading to the safehouse was left open by one of the group, which allowed a horde of infected to flood in. Ish, Susan, and a few of the children managed to escape, barricading the suburb-side entrance to the sewers. Kyle was separated from the group, where he became trapped in a room with a small group of children; the infected at the door. It is implied that he shot all of the children to save them a worse fate, before committing suicide. 
While it is unknown if Danny survived the attack, Ish managed to escape with Susan and took shelter in the suburbs, protecting a group of children. 
While Danny is not physically seen in the game, it is possible to deduce his physical appearance based on details in certain notes. A drawing displays him in what appears to be police riot gear, similar to what the military currently wears, suggesting that he scavenged a uniform from a dead a soldier. He also wears a ball cap on his head as well. He appears to have a stocky, strong build unlike Ish, who is slender and nimble.
- Assault Rifle (Possibly)
- One of the notes in the sewers is a child's drawing of two people dressed in what appears to be military colors (blue with black vests and boots), armed with rifles. The names "Danny" and "Ish" are written, along with the message "our protectors". This is the first mention of a 'Danny' in this group.
- The player can encounter two Infected dressed in military-like gear in a room not far from the main settlement. There has been some debate as to whether one of them could be Danny, though nothing has been confirmed by Naughty Dog.