kris wardle , who lives in leicester , thought his world was complete when he married his long-term girlfriend katrina in 2011 with her teenage son , mark , acting as best man .
however , the hgv truck driver would be a widower , after his beloved wife was killed in a frenzied knife attack by now 21-year-old mark after a row over his cannabis use .
kris said mark was very quiet and only interested in his computer games .