‘What it is without the hand that wields it‘ is an electronic sculpture by Riley C. Harmon.

Violence is an inevitable, mechanical function of the human brain, hard-coded down through time by culture, genetics, and evolution. Mediated experiences of killing change our perception of violence and death. As players die in a public video game server for Counter-strike, a popular online first person shooter, the electronic solenoid valves spray a small amount of fake blood. The trails left down the wall create a physical manifestation of nebulous kills.

Custom electronics based on an Atmega8/168 micro-controller are connected to a PC running a dedicated Counter-strike Source server. Players across the internet can connect and play live on the server, and each time a player dies, a java script written in Processing sends serial commands to the micro-controller, telling it to spray fake blood.

found at MAKE: Blog