German Rampage Shooter Was a Counter-Strike Player... apparently *sigh*
A 17-year-old who would give only his first name, Aki, said he had been studying this year with the shooter at a private business school, and described him as a quiet, reserved person.

Aki said the two played poker together, both in person and online, as well as a multiplayer video game called "Counter-Strike" that involves killing people to complete missions.

"He was good," Aki said."....
AND
A former classmate said... "The only thing which stands out is that Tim was always very good with weapons. He mainly shot air weapons firing plastic balls, but the house had several gun cabinets occupying square metres of walls, mainly air guns."

"He was a pretty good shooter. He used to shoot in a forest behind his house. Sometimes we'd have air gun battles in the summer."

So they blame CS rather than plastic balls .... cool