Junior Seau, a linebacker who played in the NFL for 20 seasons and was among the most widely respected players of his generation, was found dead in his California home Wednesday.

Authorities in Oceanside, Calif., said Seau, who was 43, suffered a gunshot wound to the chest and his girlfriend reported finding him unconscious. According to the Associated Press, police officials said a gun was found near Seau and his death appeared to be a suicide.

Those in professional football reacted with shock and sadness.

“It is very emotional for everybody right now,” San Diego Chargers President Dean Spanos said at a news conference. “You just don’t know what to say. There are so many things you’re thinking about that you did with him, through some good times we had here and some difficult times with the team. I think all of us are going to sit back in the next couple of days and reflect upon our relationship with him over the last years, however long you knew him. I want to remember all of the good things about him because there are so many great things about this man and what he meant. . . . He was a great leader in this community.”

Seau spent 13 seasons with the Chargers between the 1990 and 2002 seasons. He also played for the Miami Dolphins and New England Patriots. He was selected to 12 straight Pro Bowls and was named to the NFL’s all-decade team of the ’90s. He was honored as the NFL’s man of the year in 1994 for achievements on and off the field.

Former Dolphins coach Dave Wannstedt called Seau’s death “just so tragic” and “hard to believe.”

Wannstedt, now the defensive coordinator of the Buffalo Bills, said in a written statement: “He brought a sense of renewed energy and a spirit to the field, off the field, in the weight room, just everywhere that Junior went and everyone that Junior was associated with. He instilled a belief that we hadn’t reached our potential and that we could be better and he would find a way to help make that happen.

“I just feel terrible but I know how much he loved his kids. . . .Everything he was doing was centered around getting back to San Diego from Miami to be able to spend quality time with his kids. I don’t think there’s a better way a man could be remembered than in those terms.”

Several former NFL players have died unexpectedly in recent months. Last month, authorities in Richmond told Fox that former Atlanta Falcons safety Ray Easterling’s death had been ruled a suicide. Easterling was among the former NFL players involved in concussion-related litigation against the league.

Former Chicago Bears safety Dave Duerson committed suicide last year and his family filed a wrongful death lawsuit against the NFL, accusing the league of failing to properly prevent and treat concussions.

Seau was not known to be involved in any of the concussion-related lawsuits against the NFL. He survived a 100-foot fall down a cliff in his car in October 2010, a few hours after being arrested in a domestic incident. He was hospitalized but reportedly suffered only minor injuries and police said it was believed he fell asleep at the wheel.

He is the eighth member of the 1994 Chargers team, which reached the Super Bowl, to die before age 45. The others are Chris Mims, David Griggs, Rodney Culver, Lew Bush, Doug Miller, Curtis Whitley and Shawn Lee.

“He was such a great leader,” Chargers Coach Norv Turner said at a news conference. “He was such a great mentor for so many people and he has affected and impacted so many people’s lives.”

According to the AP, Seau’s mother, Luisa Seau, cried when she told reporters outside his house: “I don’t understand. . . . I’m shocked.”

She said there was no indication anything was wrong when she spoke to him by telephone this week, the AP reported.

According to the San Diego Union-Tribune, Seau’s former wife Gina said he texted her and each of their three children messages on Tuesday saying, “I love you.”

She told the newspaper: “We’re all in shock. We’re beyond sad and beyond shocked. The kids and I are just huddled together at home. There is no way to make sense of this.”

Patriots owner Robert Kraft said in a written statement: “For four seasons, after every game he played, he would always find me in the locker room just to give me a big hug and squeeze tighter than anyone I remember. It was one of the many things I enjoyed about him. He was passionate about football and always spoke with great conviction. . . . He was beloved in his home town of San Diego and quickly became a fan favorite in New England.”