Surreptitiously cussing?

I think my little darling, K4, was trying to cuss and get K2 in trouble, all in one fell swoop! The following exchange occurred between him and me:

Me: Go tell K2 dinner is ready

K4: ok.

K4 returns.

Me: What did K2 say?

K4: He said, "dammit."

Me: He said what?!?! (with alarm)

K4: He said, "dammit."

Me: I'm going to go ask him.

K4: No Mommy!! Don't talk to him! (with a bit of panic in his voice)

Me: Yeah, I'm going to go talk to K2, and you come with me.

Me: K2, did you say "dammit?"

K2: Huh? No. I said, "close the door."

Me: K4? (actually using his full name).

K4: [the tears start to flow]

Busted!

My sweet little boy, trying to pull the wool over my eyes.