A forensic autopsy was also conducted, which included an examination of the body and organs, as well as a toxicology tests and microscopic examination of organs and tissues. The final results of those tests will be part of the medical examiner's final autopsy report.
The medical examiner's office said they were awaiting the family's decision on whether to turn over Seau's brain for research.
The former linebacker was found dead in his Oceanside home Wednesday morning. Police say a woman, believed to be his girlfriend, found him in the bedroom. A gun was found near his body. Authorities did not find a suicide note in the house, but on Tuesday, the 43-year-old apparently texted, "I love you," to his ex-wife and three children and canceled an afternoon photo shoot with U-T San Diego, saying he didn't feel well.
The news stunned the football community. Fans are remembering the sports icon for his upbeat and positive personality, which is why it's so difficult for many to believe he took his own life.
"Type of individual that would actually give his shirt off his back to you, you know what I'm saying. He always reached out," said a friend Greg Allen.
Seau's apparent suicide brings to life the deaths of other NFL players who took their own lives. He is one of at least three former NFL players to have committed suicide in the last 14 months. Dave Duerson shot himself in the chest in February 2011, and Ray Easterling killed himself in February.
Seau was known for his tough tackles. Many friends and fans believe Seau's apparent suicide could be linked to brain injuries from all of those hard hits he took on the field.
"Every time you get hit, it's almost like a car wreck, they say. So I wouldn't doubt if he had major head trauma that could have made him do that," said a fan Reggie Harris.
Experts agree, saying you can't take head injury and head impact out of football.
"Even with the best helmet, you're going to have a head that's moving quickly that stops suddenly, and that's a bad thing," said Dr. Richard Besser, ABC News' medical editor.
While it is still not clear if Seau suffered the effects of traumatic brain injury, many say there needs to be more education about the possible effects of the high-contact sport.
"I think everybody is looking at it including us here with our medical staffs and such. So it is an area which is attracting attention, as it should," said Pat Haden, USC's athletic director.
Devastated fans have stopped by Seau's home to leave flowers, notes and candles. A memorial has also been growing outside Seau's restaurant in Mission Valley. Fans and friends have been stopping by leaving flowers, cards and even Chargers memorabilia. The restaurant will be closed Thursday, and it's unclear when it will reopen.
The football great was drafted fifth overall by the San Diego Chargers during the 1990 NFL Draft and played for the Chargers until 2002. He went on to play for the Miami Dolphins from 2003 to 2005 and the New England Patriots from 2006 to 2009. Seau was also a standout player at University of Southern California.
When he played for USC, Seau wore number 55, and that number now holds a special significance.
"His number 55 took on great significance. The moment he wore number 55, it's been a special number," said Haden.
Seau helped carry the Chargers to their only Super Bowl in 1994. He is now the eighth player from that Super Bowl team to die. The causes of death in those players range from heart attacks to a plane crash to a lightning strike.
In addition to football, Seau -- an Oceanside High alum -- was known as a generous philanthropist, focused largely on helping youths. He is survived by a daughter and two sons.
The Associated Press contributed to this report.