The Teddy Bear is in the water closet on the Eastern side of the lake. It's behind a barricaded door so you'll need to use the Axe or the Gasoline to get inside.

If you place this in the path of the Baby Killer, he will pick it up and try using it as a weapon, causing you no damage or interruption. The drawback of using this is that the Father will arrive much quicker from your first attack.