20-year-old Chris Staniforth was killed by a pulmonary embolism. It's essentially a large, artery-blocking blood clot, and can most likely occur if someone sits in the same position for several hours.
Staniforth had no pre-existing medical conditions, but he did have a dangerous habit of playing Xbox for up to 12 hours at a time, "sucked in playing Halo online against people from all over the world," his father told AFP.
A story like this is certainly a cautionary tale, but not a caution against video games. The real danger wasn't the Xbox, it was the fact that Staniforth remained sedentary for long hours.
If you want to protect yourself or a gamer you love, encourage them to keep gaming sessions short (good for your body and your eyesight).
If you find yourself in the middle of an addicting multiple-hour gaming marathon, make sure to take several small breaks to get up and walk around the room. Even just a trip to the kitchen for a glass of water could save your life. If you need help stopping for breaks, try one of these recommended time management apps.