Police responded after a female, believed to be Seau's girlfriend, found him in the bedroom with a gunshot wound to the chest at about 9:35 a.m. The 43-year-old was declared dead at the scene. Oceanside Police Lt. Leonard Mata said a handgun was found next to the body.
Police say there was no suicide note found at the scene. The death is being investigated as a suicide.
"(The girlfriend) was there this morning. She did leave for the gym. When she came back, she found Mr. Seau," Mata said.
San Diego Chargers Chaplain Shawn Mitchell said he was meeting with the family. The family was seen hugging and crying outside the home. Seau's grief-stricken mother addressed reporters, thanking the public for showing love for her son.
"As great as a football player that Junior was, he was a greater human being," Mitchell said. "Very philanthropic, gave away thousands upon thousands, always had a smile, never turned down an autograph."
Seau was considered the best linebacker of his generation. He 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.
"Junior Seau was a San Diego original. While he was most known as one of the best linebackers of all time, his passion on the football field was matched by his commitment to San Diego, and particularly its children," said Jamie Ellis and Jason Gurka of the Junior Seau Foundation in a statement. "All of us at the Junior Seau Foundation are devastated by the loss of our founder, leader and friend."
Seau was not without troubles. In October 2010, Seau was arrested on suspicion of domestic violence, then drove his SUV off a cliff in Carlsbad after being released from jail. The former Chargers linebacker was found by emergency crews on the beach. He told authorities at the time that he had gotten sleepy.
Seau is one of at least three former NFL players who have committed suicide in the past 14 months. Dave Duerson shot himself in the chest in February 2011, and Ray Easterling killed himself in February.
Seau's former teammates and friends are mourning the loss of the football great.
"It was devastating. I just broke down and cried, and just have had knots in my stomach all day," said Rodney Peete, Seau's friend and former teammate at USC.
The NFL Players Association said in a statement, "The 12-time Pro Bowler achieved a level of success on the field that is unparalleled and his off-the-field service accomplishments are beyond admirable. ... The NFLPA player family today joins with the Seau family to mourn a brother lost too soon."