Games : How do you take down a Paladin with the MAAWS

I have completed every single Weapon Master challenge except this one. I need to take down 2 more Paladins with the Maaws (I have no idea how I got the first one...must have been already injured and I got lucky...)

I watched this video:

If the link to the video is ever destroyed, the player shoots the Paladin with an assault rifle with a few clips. It even shows him getting hit markers like crazy, and then he hits the Paladin with a single shot from the MAAWS and it goes down.

But it doesn't seem like I can hit the Paladin with bullets, even when I'm on the same side of the map that it is on.

So here I am, asking for help on the final challenge. How do you take down Paladins with the MAAWS launcher? (I already did it with the MAYHEM thankfully...)