strange behaviour

I'm sitting here in the living room, Em is on the arm of my chair.. Ollie is across the room from me on the cat tree.. jack is on the floor in front of the cat tree. All of a sudden Ollie starts talking.. he slowly jumps down from the tree. walks over to jack, and "pounces" on him.. in very SLOW motion the whole time talking., ollie tries to 'tackle" jack. all the time chattering. Jack puts up one of his back legs to ward him off. jack just looks away.. Ollie lets go for a second.. jack jumps up on the tree. Ollie is still chattering away..

now get this..Em.. my elderly kitty.. jumps down, saunters over to ollie, and bites him. I've NEVER seen her do that. after a very small uneventful tussle, the hostilities and chattering has ended. Jack was sitting on the tree (and is now on the platform eating) and Em and ollie are laying on the floor. this took all of a minute and a half..

I wonder what that was all about.

(update 2016 - yes, well looking at this now it is pretty clear that we had some "I'm in charge" moments going on here.. )