Police confirmed Belcher's identity to ABC News Radio Saturday morning.
Officials say Belcher shot his girlfriend, 22-year-old Kasandra M. Perkins, inside a house on Saturday. Perkins' mother called police, saying her daughter had been shot multiple times. Police did not release a possible motive. Authorities say Belcher and Perkins have a 3-month-old child, and the couple had been arguing recently.
Police say Belcher then drove about five miles to the team's practice facility at Arrowhead Stadium, where he reportedly committed suicide by shooting himself in the head in front of his coach and general manager.
Police Spokesman Darin Snapp said that before turning the gun on himself, Belcher thanked Chiefs general manager Scott Pioli and coach Romeo Crennel for all they had done for him.
The Chiefs issued a statement confirming there was an incident at Arrowhead, and they are cooperating with authorities.
"The entire Chiefs family is deeply saddened by today's events, and our collective hearts are heavy with sympathy, thoughts and prayers for the families and friends affected by this unthinkable tragedy. We sincerely appreciate the expressions of sympathy and support we have received from so many in the Kansas City and NFL communities, and ask for continued prayers for the loved ones of those impacted," said Chiefs Chairman and CEO Clark Hunt in the statement.
The news cast a pall over the organization as it prepared to play the Carolina Panthers on Sunday. The Chiefs released a statement Saturday afternoon saying the team will play the game at its originally scheduled time.
The stadium has been locked down since 8 a.m. local time.
Belcher was a 25-year-old native of West Babylon, N.Y., on Long Island, and played college ball at the University of Maine, whose coach Jack Cosgrove released following statement Saturday afternoon:
"His move to the NFL was in keeping with his dreams," Cosgrove said in the statement. "This is an indescribably horrible tragedy. At this difficult time, our thoughts and prayers are with Jovan, Kasandra and their families."
According to the school's statement, Belcher was named the 2008 CAA Preseason Defensive Player of the Year during his senior year and also named to the Preseason All-CAA Team. The school says Belcher's stats include 293 tackles, 44.0 tackles for loss and 18.0 sacks over 44 games.
According to the statement, Belcher graduated the University of Maine in December 2008 with a bachelor's degree in child development and family relations.
Belcher had played all four of his NFL seasons for the Chiefs and played in every game each year, including the 11 so far this season.
ABC News and the Associated Press contributed to this report.