When someone consumes excessive amounts of alcohol, breathing slows and the brain is deprived of oxygen. The struggle to deal with an overdose of alcohol and the lack of oxygen will eventually cause the brain to shut down the body functions that regulate breathing and heart rate. When that happens, the drinker can die.
Rapid, excessive drinking is especially dangerous because people can consume a fatal amount of alcohol before they lose consciousness. It's best to always drink in moderation and avoid taking part in drinking games that involve drinking excessive amounts or drinking rapidly.