OMG! Cat drama!

The cats have gone insane. Or rather, Ohno has gone insane. For the past two days, Ohno has been attacking Spike. Unprovoked (as far as we can tell) and unrelenting. They have always been good buddies, but yesterday, out of the blue, Ohno went after him and the sound made my heart stop. Since then, we have taken to locking one or the other up in the master bedroom. I don't know what to do. Anyone ever heard of this? They are both male, both fixed. There are no females in the house. I am at a loss. All the kitties are wigging out due to the tension. *sigh*

( I saw The Last Kiss today. Cut for the yada, yada and spoilers. )