Another ex-player, former Atlanta Falcons safety Ray Easterling, who had joined in a concussion-related lawsuit against the league — one of dozens filed in the last year — shot himself last month at age 62. His wife has said he suffered from depression and dementia after taking years of hits.
Seau's ex-wife, Gina, told The Associated Press on Wednesday that he sustained concussions during his 20-year NFL career, during which he also played for Miami and New England.
Mitchell said he never heard Seau complain about dizziness or headaches.
"With Junior, that would be so outside of his nature because he had an amazing threshold for pain," Mitchell said.
Family members and friends have said they weren't aware of any issues that may have led to Seau's suicide. Police said no suicide note was found.
"This is not anything I thought he would ever do," former San Diego Chargers safety Miles McPherson said.
Associated Press writer Elliot Spagat contributed to this report.
Copyright 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.