We still do not know what led a football player to kill his girlfriend and himself.
According to a sports psychologist, stress and pressure can drive a person out of control.
Robert Andrews, a sports psychology consultant, said the most vulnerable are usually athletes, particularly football players, given their lifestyle.
"You have all kinds of people wanting their time, their money, their resources, so there's all kinds of things that are pushing in on these athletes and causing them all kinds of stress and pressure," Andrews said.
Sources close to Jovan Belcher believe those two factors may have led to what happened over the weekend.
The 25-year-old Kansas City Chiefs linebacker killed his girlfriend, the mother of their infant daughter, before turning the gun on himself, investigators said.
Belcher is the fourth football player this year to commit suicide. In July, O.J. Murdock died of a self-inflicted gunshot wound. Before that, Junior Seau did the same. Earlier in 2012, former Atlanta Falcon Ray Easterlings' death was also ruled a suicide.
Each case may be different, but Andrews said a healthy, strong team starts before the game.
"It's not just the type of athlete. They're looking at personal ethics and morals and how they handle their life on and off the field. I think it boils down to, what are you doing to win? What are you willing to do to win? How much are you willing to accept and tolerate to the scope of winning?"