"My brother was a loving brother," Junior Seau's sister, Annette, told reporters as she asked for privacy as the family grieved. "He was a caring citizen."

Before the Chargers made him the No. 5 overall selection in the 1990 NFL Draft, Seau was an All-American at the University of Southern California. Those in the Trojans program were as shaken as many of his former NFL colleagues.

"This is a very sad day," USC head coach Lane Kiffin said in a statement. "The USC football program and the entire Trojan Family extends our condolences to Junior's family. He was one of the greatest Trojans of all time. Our team and fans were very fortunate to see him just a couple of weeks ago at our spring game at the (Los Angeles) Coliseum. He will be deeply missed."

The Patriots, where Seau ended his 20-season NFL career in 2009, said in a statement they were "shocked" about Wednesday's developments.

"We were fortunate to have had Junior join the Patriots in 2006 and are thankful for his many contributions to the team over the next four years," the Patriots said. "He had a legendary NFL career, and his unrivaled passion for the game quickly made him a fan favorite here in New England. This is a sad day for the entire Patriots organization, our coaches and his many Patriots teammates. Our heartfelt thoughts and prayers go out to his family and his many friends who will mourn this loss."

Chargers head coach Norv Turner worked with Seau in San Diego and Miami.

"I have no words to describe the passing of Junior Seau," Turner said. "It is a sad, sad day not only for me but for the whole sports community. . . . I can tell you no one had more character and true leadership ability than Junior. He brought passion to the game of football that was unmatched.

"His commitment to charitable causes in the community was inspiring. It was an honor to know him. My thoughts and prayers are with his family."