1.
SIA is basically a Gaming term in computer world, refering to real life term - KIA.
It's very alike with word skillad, meaning Skilled In Action. It's Killing with Skill = S-killing.
Being SIA in first person shooters has a meaning of being shot in a very unorthodox, very thought through and
amazing way.
SIA can be anything including Headshots, Clutches, ACEs, and other
amazing stuff that can be done using skill.
2.
SIA'd also
may have a meaning of " Served in action " linking to " you got served " .
Gamer
chit-
chat:
(two guys watching their teammate
frag):
- Woah, look at that HS !
- Ahahaha, another one !
- Holly shit, those guys got SIA'd :DD
...