If you go to http://www.ninwiki.com/Year_Zero_Timeline and scroll down to 2/9/0000 or 2/9/2022 it says that "Angry Sniper" shoots people at baseball game in Chicago in act of "resistance."
Then if you open a new window and go to http://www.ninwiki.com/World_Of_Year_Zero_Fact_Sheet and scroll down to the Attacks and Wars section it says: "The 105th were all killed in a nuclear attack, the location is unknown." By the location of this information it seems as though they were all killed in 2009.
When you listen to BallgameOver.mp3 or read about it, the "Angry Sniper" says: I used to be a sniper, 105th airborne crusaders, AMEN.