Feivel does it again. Sigh.

Just when he was going along so well, in terms of behavior.
This morning I called to Gilad when I was leaving, part of our daily ritual, so he can come give me a hug and a kiss. Mommy isn't allowed to leave without her hug and kiss from Gilad of course. For some reason this morning Feivel decided he needed to say goodbye to me too so he barrels down the stairs.
He crashed into Gilad and sent his little brother actually tumbling. I watched Gilad hit a wall, turn 180 degrees, hit his head on a middle step, turn over another 180 degrees and land at the bottom of the stairs upright (more or less).
Miraculously, Gilad was unhurt, just frightened.
I don't know what to do with Feivel. I know it was an accident. Sooner or later though one of his "accidents" is going to seriously injure someone. Gilad could have been badly hurt, even paralyzed this time. I don't know what might happen next time.
It's scary. I don't know how to stop Feivel from doing this sort of thing. He doesn't mean it. He just has no way of performing reasonable control, and he's getting big.