Omg, I have it...we make it a pseudo the good-the bad-the ugly situation:

So, assassination takes place, perhaps with a minor riot or some sort of panic caused by the Taja; All three characters end up having to rush out of wherever they are, stopping (perhaps with a few weapons at the ready) in the same alley (XD, actually this is making me think of the scene in Conan The Barbarian, when all three thieves bump into one another in the night). Momentary distrust ensues, or just confusion in general, before they realize that (for some relevant reason) they'll have to at least temporarily work together.

Danger passes, they go their separate ways again, but due to other relevant reasons, they end up having to work together at a later date? It's one hell of a coincidence, but I think it'd be kind of dynamic to have them meet, split, and reunite again. If anything, one character could just force their way into getting another to help them, and then that character could remember that the third has something that could help the party as a whole...at least, for a little while; the alliance should still be shaky enough that the characters *can still split up if they feel disgusted by one another...plus, drama.

(Won't be able to finish the post tonight, but it'll be up by tomorrow afternoon.)