He will enter a school filled with happy children, excited that it is the first day as teacher's assistant. The kids are about kindergarten age. Population 1 has a lot of fun, helping out, seeing that the kids all get what they need and are all behaving themselves. Then, the main teacher baked a fresh batch of cookies.
In the manner you would expect in this situation she beamed in her cheery British accent, "Hey kids, I brought you some cookies!" Population thought they looked delectable, delicious, extra chocolatey, crispy and crunchy for the taking. The kids are cheerfully beamed long awaiting snack time.
Then, a monotone voice interrupted the jubilee, "I like trains..." It was a blankfaced young boy, about the same age as the other kids. Population 1, the kids, and the teacher all just stared at the kid. Then as if on cue, all of them got hit by a train.