World of Warcraft chat. He did so because he assumed that those chat logs were less likely to be saved.
Kruse Wellwood and Cameron Moffat spent time planning the assault beforehand, and Wellwood even mentioned his desire to do the crime to a guild friend in WoW. Following the 2010 crime, Wellwood logged back in World of Warcraft to talk about the murder to his online girlfriend in Halifax, sending her links of the news reports as proof of his story. Amazingly, his girlfriend mildly chided him to "just don't do it again."
The in-game chat logs were part of the mountain of evidence collected by the police. The pair pleaded guilty to the crime.