His mother, who heard gunfire as she stood in the kitchen, rushed to her son's bedroom and watched his remorseful goodbye.
Belcher apologized to his mother, kissed his 3-month-old daughter and fled his rented home in his Bentley, Mo.
The Kansas City Star learned those details and others from multiple police sources Monday as officers continued their investigation into why Belcher, 25, killed his live-in girlfriend, Kasandra Perkins, 22, on Saturday morning. Arguments over relationship and financial issues had simmered for months between them, according to the sources.
Belcher's mother, who came from New York to live with her son so the couple could work through their issues, didn't hear much of the argument. But just before 8 a.m., she heard her son say something to the effect of: "You can't talk to me like that!"
Then she heard gunfire.
Afterward, Belcher drove to the only place he felt safe -- to his other family at Arrowhead Stadium, police said.
As he covered the five miles from his home to the stadium, his violent act weighed on him, police believe.
"He probably realized he had done something and he couldn't go back," Police Sgt. Richard Sharp said.
In the parking lot of the practice facility at 1 Arrowhead Drive, Belcher encountered Chiefs general manager Scott Pioli. Belcher stepped out of his car with a gun pointed at his own head, police said.
"I did it," he said, according to police. "I killed her."
Club officials knew about the couple's problems. The Chiefs had provided counseling and "were bending over backward" to help, Sharp said.
But Belcher told Pioli that the assistance wasn't enough to fix their problems and now, "It was too late."
When another Chiefs employee arrived, Pioli told him to stay back.
Meanwhile Pioli tried to persuade Belcher to lay down the weapon, Sharp said.
Belcher thanked Pioli for everything he had done for him. He asked if he and Clark Hunt would take care of his daughter.
Chiefs head coach Romeo Crennel and linebackers coach Gary Gibbs arrived in the parking lot and Belcher reportedly announced, "Guys, I have to do this."
Crennel tried to dissuade him.
"I was trying to get him to understand that life is not over," Crennel told The Star. "He still has a chance and let's get this worked out."
As Pioli and Crennel tried to reason with Belcher, the men heard police sirens closing in. Belcher then walked a few steps away with the gun still pointed at his head.
"I got to go," Belcher reportedly said. "I can't be here."
Belcher knelt behind a vehicle and made the sign of the cross across his chest before firing a single bullet into his head.
Kansas City police believe Belcher killed himself because he was distraught over what he had done to Perkins.
"He cared about her," Sharp said. "I don't think he could live with himself."
The night before the killings, Perkins had attended a concert downtown with friends, and Belcher had "partied" at the Power and Light District, police said. It was unclear when they arrived home, where Belcher's mother was watching their baby. A woman who answered Belcher's mother's cell phone Monday declined to comment.
Detectives don't know what specifically sparked the argument between the couple at home, but a friend of Perkins told The Star that the couple argued around 1 a.m. Saturday when Perkins returned home from the Trey Songz concert and drinks with friends afterward. Belcher was mad she had stayed out so late, the friend said.
Sometime later, Kansas City police talked with Belcher after finding him asleep in his car on Armour Boulevard. Officers determined he was able to drive himself home. Police believe he arrived home about 7 a.m., well before a 9:30 team meeting. That's when the yelling began.
Police said youth, immaturity and financial pressures served as a backdrop. During his college years, Belcher allegedly punched a dormitory window because he was upset over a woman.
Autopsies with toxicology tests were performed on both bodies, but results will take weeks, police said. Investigators believe alcohol may have played a role in the argument's escalation.
Police recovered several legally owned guns from Belcher's home.
Investigators were testing each one, and the gun found with Belcher's body, against shell casings and bullets they recovered.
Police spokesman Darin Snapp said Monday that Belcher's mother, who had been staying with the couple, was given temporary custody of the couple's daughter. But he said it was unclear if the grandmother and baby were still in the Kansas City area.
Perkins, who grew up in Texas, met Belcher, who grew up in New York, through a cousin, Whitney Golden Charles, the wife of Chiefs running back Jamaal Charles. Perkins moved to Kansas City in 2010 to be with Belcher. Her relatives learned of her death from the news, police said. A woman who answered the phone at a relative's home Monday declined to comment.
Monday afternoon, the family issued a statement that spelled Perkins' first name with a double s, though she spelled it with one on her Facebook page:
"On behalf of the Perkins Family, we appreciate the outpouring of love and concern for our Kassandra 'Kasi' Perkins. Our hearts are truly broken for Kasi was a beloved daughter, granddaughter, sister, mother, cousin and friend. ... Please keep us in your hearts and prayers as well as the Belcher family for two lives were loss. Again we thank you for your support, our wish is for Kasi to be remembered for the love she shared with us all. Kasi will be truly missed!"
Jamaal Charles also released a statement: "Our family has suffered a personal tragic loss ... As this is a very tough time for our family, I ask that we are respected as we grieve. Kassandra was not only family, but a friend and a loving mother. As my actual family and my Kansas City Chiefs family have been altered forever, we ask that you keep us and most importantly their child in prayer. Thank you all for your continued support."
Randy Covitz and Adam Teicher of the Kansas City Star contributed to this report.
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