It doesn't matter, you DON'T tell ANYBODY you hired a hitman. especially not when the hitman is your debtor who has ZERO reason to shut the fu** up if he get caugh.
It's not J reaction that matters here but the fact someone who has the staff and the brain to carry out a plan like this CAN'T be dumb enough to admit it the very same day.
Plus, he know J pretty well and his temper, that's what he used against him before. And he already know J is a mess because of KD is on the brink of death, so the whole little chitchat is just useless, dumb, and peak "mistake" forced on to a character to solve a problem, aka J needs to find out somehow who did it..:
I don't now why the rush, but it could have been solved in literally the next chapter, like, the cops catch that bas**** and he woud have just spit out everything during the interorgation, so...
This whole thing is really just dumb and unnecessary and pointless and the worst type of writing...
Im really disappointed.