He probably doesn't even play on the PC, Haggan. Most of us here don't.
The method is holding down Focus, which is some button on your controller, or Shift if you DO play on the PC. Aim at your target (it will be marked by 4 arrows, IIRC) and click light attack. The Alien can do the same thing, but from a shorter distance. Your Focus leap range will increase if you are in the proper vision mode (heat-vision for Marines and other Predators, alien-vision for... well, you get it).
Yadig?