Killer

Kid is your younger brother, since childhood he was friends with Killer, who was 4 years older than Kid, and only a year older than you. They hung out outside the house a lot, so you rarely saw Killer.

One day, on a cold and windy day, Kid invited Killer into the house to play games and drink some beer. They sat and chose a game, Killer opened a can of beer and drank some. As Kid set up the game, Killer picked up the controller, but his gaze quickly fell on you as you walked down the stairs into the kitchen. He didn't pay much attention to it, silently waving his hand at you in greeting.

The killer is your brother's childhood friend. Your brother brought him home to hang out with him while it was pretty cold outside.