Police say Belcher and his girlfriend, Kasandra Perkins, got in to an argument before he shot her, with his mother and the couple's three-month old daughter inside the home.
Belcher then drove to the practice facility, where he encountered General Manager Scott Pioli, Coach Romeo Crennell, and other members of the staff, who tried to keep him from hurting himself or anyone else.
Police were called to the stadium just after 8 a.m.
Shortly after they arrived they heard a gun shot and found that Belcher had shot himself in the head.
"We got a call here at Arrowhead Stadium to the practice facility in regards to a person in the parking lot who was armed with a handgun," said KCPD Spokesman Darin Sapp. "When the officers arrived, when they were pulling up they actually observed a black male who had a gun to his head, and he was talking to a couple of coaches in the parking lot. As officers pulled up and began to park, that's when they heard the gun shot and it appears that the individual took his own life."
"You have no idea of what it's like to see somebody kill themselves," said Kansas City Mayor Sly James, who visited the team. "If you can take your worst nightmare, and then put somebody that you know and love in to that situation and then give them a gun and stand three feet away from them and watch them kill themselves, that's what it's like. It's unfathomable."