Samsung Galaxy Note 5 stays lit after "OK Google" command

[AC Question]

Let's say my phone is locked. Screen is black. I say "OK Google" and the phone lights and the "listening" thing comes on. I make some sort of command, like "what is the weather going to be today". After it is done telling me...the phone stays lit. The screen never goes dark again. Actually, I think it does for a second, but then it lights back up again. I think Google is still listening and every time it hears ANYTHING it lights back up. But how do I tell it to lock? I've tried literally telling it to lock the screen, but it just gives me info on how to do that on other devices.