EDIT: There's an earlier spot you can get this - read the comments.
I got this in The Mountain Temple mission which is after you leave The Hidden City. When you're inside the blood sacrifice area, you'll see a whole bunch o' priest dudes dressed in ceremonial gear, there's probably about 6 of them all armed with swords.
If you head to the point in the video, there's a pool o' mud in front of the area Lara is hiding; put on the mud (
) and then hide against the wall. Now wait for some poor unsuspecting soul to come close. I killed a dude first to get them all riled up.
https://xboxdvr.com/gamer/sneakystabbalot/video/60373185