Hanson, who spent most of his career with the Braves, had trouble breathing Sunday when he was rushed to an Atlanta hospital, and he was in a coma Monday due to catastrophic organ failure, CNN affiliate WSB reported, citing unnamed sources.
The station didn't state what caused the organ failure or his death
CNN couldn't immediately confirm the affiliate's account, and the Atlanta hospital where Hanson died didn't immediately return a message.
The Braves' front office confirmed Hanson's death, and Major League Baseball's website reported
that some of Hanson's former teammates were near him when he died at Piedmont Hospital late Monday night.
Citing an unnamed source, the league also reported that Hanson had difficulty breathing Sunday morning and was taken to a hospital.
"We are incredibly saddened to learn of Tommy's tragic passing," Braves President John Schuerholz said in a statement. "He was a favorite in the clubhouse and with our staff and he will truly be missed by everyone in Braves Country. Our thoughts and prayers are with his wife, family, former teammates and friends."
A 6-foot-6 right-hander nicknamed "Big Red" for his hair and beard, Hanson played for the Braves until 2012. When he began suffering shoulder and back injuries, he was traded to the Los Angeles Angels. Earlier this year, he was working his way again through the minors.
Braves shortstop Andrelton Simmons took note of Hanson's personality.
"Very sad to hear about Tommy Hanson. Wish his family and close friends a lot of strength. He was a really nice dude," Simmons tweeted.
Chipper Jones, who retired from the Braves in 2012 after 19 seasons, was grieving about his onetime teammate.
"My heart is broken today. Tommy Hanson was a great teammate, friend and pitcher. We all loved and pulled for him. We ALL will miss him," Jones tweeted.
Past Braves players such as Dale Murphy also mourned Hanson on Tuesday.
"Sad day in @Braves country today. Prayers out to Tommy Hanson's family and friends. RIP Tommy," tweeted Murphy, who retired from baseball in 1993.
The only other major league team where Hanson played was also expressing sorrow.
"Tommy Hanson was a man with a big heart, constant smile & a greeting for all. Prayers & condolences to his family," the Angels team tweeted.
What is catastrophic organ failure
The medical name for catastrophic organ failure is MODS, which stands for multiorgan dysfunction syndrome. In short, it means a person's systems are short-circuiting. Any number of medical conditions can lead to MODS, including infection or an underlying illness.
It's not known what caused Hanson's organ failure, but it is rare in an otherwise healthy person, according to Dr. Darria Long Gillespie, an emergency room physician with Northside Hospital in Atlanta.
MODS carries an extremely high risk of death. Once one organ starts to fail, it triggers failure in other organs.
"MODS is the final pathway for a number of different causes," Gillespie said, drawing the analogy of a building collapse, which "could be caused by any number of things, including a fire, earthquake or demolition."
"Similarly, MODS can have many different causes that lead to the same outcome," she said.
Hanson's career record
Hanson finished his career
with 49 wins and 35 losses, a 3.80 earned run average and 648 strikeouts, according to Major League Baseball's website.
He broke into the majors in 2009, finishing third in the National League Rookie of the Year voting that year with 11 wins and a 2.89 ERA for the Braves.
Hanson last played professionally in the Giants' minor league system earlier this year.
"Tommy was a great talent with a bright future who was taken from us well before his time," the Giants said in a team statement. "Our thoughts and prayers are with his family and the many people who were lucky enough to know him."
In a 2006 interview with a Major League Baseball writer, Hanson said he liked to throw a variety of pitches -- fastballs, sliders, curves and changeups.
"My whole pitching mindset is to go right after hitters, to attack them. I don't like to fall behind hitters, and I don't like to walk hitters. It is about making them put the ball in play," Hanson was quoted as saying on the league's website.