and last may just 28 years old, derek boogaard died of an overdose of medications and alcohol. researchers later determined he had a degenerative condition similar to alzheimers caused by repeated blows to the head. boogaard's story has been chronicled this week in a three-part series in the "new york times". we're joined now by john branch. a sports reporter for the "times" and author of the series. and dr. robert cantu of the boston university school of medicine, one of the researchers who studied boogaard's brain after his death. john branch, so this was a man who rarely if ever scored a goal, couldn't skate fast but was a crowd favorite and a kind of star in a particular way. explain that role for those who don't follow sports. >> sure. the enforcer is a guy who maybe doesn't have the greatest skills but he's usually a big guy. he treats... he's treated as a body guard for the other team members. when they have... if they start to get roughed up by the other team they send out the enforcer. that's their body guard. >> brown: derek boogaard told his mother, he said it's my jo