It is likely that Mr. Peterson was doing one of the following exercises:
- Barbell Decline Bench Press
- Barbell Flat Bench Press
- Barbell Incline Bench Press
- Guillotine Bench Press
There are inherent dangers in having a weighted bar near one's neck. This makes a training partner or spotter that much more important on heavy sets. Training partners are good enough for elite powerlifters, and they're good enough for you. (I realize finding a good training partner can be very difficult. The point is just find someone to cover you when the weight gets up there.)
Doing dumbbell bench presses avoids the risk of asphyxiation since the bar element is removed. Other risks remain, though. In a state of fatigue, a person could drop a dumbbell or otherwise lose control, with severe consequences.
Strength training is a wonderful endeavor. Learn from this tragedy to pursue it safely.