What's far-fetched about small children, who just witnessed a horrible act, not thinking clearly?

You said in another comment that the kids missed the firehouse completely as they were running from the school. That's not what happened. In the bus driver's statement, she says she saw them in the parking lot of the firehouse. That's when Rosen came, and they all went to his house.

So, they didn't miss the firehouse, that's where they were found by the bus driver.

What's far-fetched about small children, who just witnessed a horrible act, not thinking clearly?