But Seau, 43, a star linebacker at USC and for his hometown San Diego Chargers, apparently ended his life Wednesday with a self-inflicted gunshot wound at his Oceanside home.
McCoy said Seau died of a gunshot wound to the chest. A handgun was found near the body. The case is being investigated as a suicide, although police found no suicide note. A crowd of media and onlookers gathered outside the home Wednesday morning.
Seau's ex-wife, Gina, said that on Tuesday he sent her and each of their three children — daughter Sydney and sons Jake and Hunter — a text message, ending with "I love you."
Seau, an All-Pro linebacker who spent most of his 20-year NFL career with the Chargers, retired in 2006 and then "unretired" several days later, saying he was not ready to leave a game that he loved. He retired for good after the 2009 season.
On Wednesday, some saw similarities between the deaths of Seau and former Chicago Bears safety Dave Duerson, who died of a self-inflicted gunshot wound to the chest last year. In a suicide note, Duerson had asked his family to donate his brain to the Boston University School of Medicine.
Researchers from that school later determined that Duerson suffered from a neurodegenerative disease linked to concussions, and that played a role in triggering his depression. The San Diego County medical examiner said an autopsy for Seau is set for Thursday.
Seau will be remembered as one of the greatest players in NFL history at any position, a 6-foot-3, 248-pound wrecking ball who made the Pro Bowl 12 years in a row and was voted All-Pro 10 times. He often veered from the script on the field, and that only made him more effective.
Christian Fauria, a longtime NFL tight end, said opposing offenses frequently could not rely on scouting reports when it came to lining up against Seau.
"Most of the time he would just kind of go where he thought the ball was going," Fauria said. "He would disregard every bit of coverage rules and gap assignments. He would just go to where he thought the play was going, based on what he looked at, what he saw."
That was the case at Oceanside High, where Seau dominated in football, basketball and track, and at USC, where his No. 55 jersey became synonymous with the gold standard of linebackers.
He had humble beginnings with the Trojans, however, having entered the school ineligible for his freshman season because of low test scores coming out of high school.
He later said he initially felt like an outsider at the school and harnessed that as motivation.
"It was terrible," he told The Times in 1991. "I used to walk the campus and not be part of the inner circle. I had no friends. The guys would be mingling on the steps, and that would be the inner circle and they didn't accept me. They were USC. They were the players, and they were looking at a guy who didn't pass his SATs."
After an ankle injury limited his contributions as a sophomore, Seau broke through as a junior and became a unanimous first-team All-American. He made the then-rare decision to forgo his senior season and enter the NFL draft.
"It was a money decision," he later explained. "I had the security of my mom and dad in my hands. I don't know how my dad made it, paying the bills while we were growing up, but I owe everything to him and my family."
The Chargers made the 20-year-old Seau the No. 5 pick in the 1990 draft, worried only that he might be gone before they had a chance to select him. As was the case at USC, Seau did not feel immediately embraced by his teammates. He felt shunned because he was a contract holdout in his first training camp.
He experienced an attitude shift in the seventh game of his rookie season, against the Los Angeles Raiders, when he had successfully called a defensive huddle. His team was not victorious on that day, but, in a way, Seau was.