Through most of his career he avoided negative publicity that plagued some in the NFL.
But in October 2010, he made headlines when he was charged with domestic violence after an incident with his girlfriend, and then hours after his arrest he drove off a cliff and crashed on the beach. Investigators later ruled the crash an accident, saying he fell asleep at the wheel.
On Wednesday, Seau made headlines again. His girlfriend, who had just returned home from a workout, found him in the bedroom of his home with a gun lying next to him, authorities said.
It is not clear if Seau left a note or an explanation. Funeral arrangements are pending.
In the hours before his death, Mitchell said he sent text messages to his ex-wife and their three children.
"They said simply, 'I love you," Mitchell told CNN. "They actually responded back to him with 'Love you too, Dad.'"
Alan Duke reported from Los Angeles, and Chelsea J. Carter reported from Atlanta.