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For 20 seasons Junior Seau fist pumped the crowds and held the line on the football field. The NFL superstar wore the jersey for New England, Miami and perhaps closest to his heart, his hometown of San Diego. Chargers fans and fellow footballers were stunned when news broke on May 2, 2012 that Seau had committed suicide.

The 43-year-old's mother was understandably shaken when she talked to reporters outside Seau's California home. It was visible heartache for a woman whose son escaped death in 2010, when Seau survived a car crash off a cliff. He later told police he'd fallen asleep at the wheel.

Seau's death is adding pressure to the NFL to study the effects of concussions on player's brains. In 2011, Dave Duerson of the Chicago Bears committed suicide after making a heart-wrenching request to have his brain donated for injury research.

While experts are exploring any links to injuries on the field to long-term mental damage, fans are grieving the loss of these gridiron greats.