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...)

Update

I was just playing around on the Combat Readiness Program, and a Paladin was called in, on Riot. It seems like that Paladin was physically lower than most that I've seen. I was able to hit it with a KF5, so probably any gun would do. So now to figure out what maps have paladins that are low enough to shoot at... Hopefully I can get someone to get one on Riot so I can confirm it still works when playing online.