During the level VENICE, you'll want to play the mutant shooting mini-game before entering the sex shop / strip club. You'll need to complete 3 rounds of the mini-game to win the final prize which is a teddy bear. It is recommended that you use a fast shooting weapon like the 6-round shotgun, or a good automatic rifle.
After picking up the teddy bear, walk to the end of the hall and find the boy. Giving him the teddy bear will unlock the achievement.
*Posting for Maka91, because he is only playing the digital version.