His early life is given to Niko through Eddie Low, where he claims he was abused as a child by his father, and was a strange kid when growing up, attempting to molest and sexually abuse other kids.
Throughout Grand Theft Auto IV, Eddie Low's crimes are reported on the radio, although the police are unaware of his true identity, and are unable to come up with a nickname for him. His crimes include murdering and beheading joggers. He also has an online blog which details his insanity, although surprisingly doesn't have any followers.
When his random encounter can be unlocked, Niko first comes across Eddie when he asks him to help him dump a duffel bag (which contains the head of a jogger). Niko reluctantly agrees, and Eddie sees Niko as a friend and begins to share some of his disturbing fetishes, which freaks Niko out. After Eddie dumps the bag in the docks, and Niko drops him off.
Sometime later, Niko encounters Eddie once again, when Eddie is lurking in a dark alley. Niko is taking aback by Eddie's disturbing comments, such as when Eddie asks Niko if he wants spanked. When Niko tells Eddie to fuck off, Eddie goes into rage and tells him how he brutally murdered children. Then he attempts to kill Niko with a knife, but Niko kills him in self defense and gets away. Eddie's body is later found and identified, and he is tied to the murders.