http://www.youtube.com/watch?v=rIOOgFUwZfA&feature=g-u-u
AT 2:30
He throws 3 Plasma grenades! 
HE HAS THE SPECIAL TACTICAL PACKAGE EQUIPPED
Yeah, because of the Tactical Package he equipped.
Or he could have just picked one up while walking…
No xD, it says 3 At the grenade count at the top left of the screen
Oh, OK, didn’t notice that, well, as the first guy said, it’s probably just be a mod “XD”.
Yay, I can laugh even harder as I/someone else wastes all 3 Plasma Grenades miss their target because we’re flailing around in a close-range Pistol/DMR duel!