Kansas City Chiefs linebacker Belcher also complained about Kasandra Perkins, the mother of the couple's three-month-old daughter, in conversations and text messages sent to a woman he was dating on the side, newly released police reports show.
In one text message sent in late October or early November, Belcher wrote he "would shoot" Perkins "if she didn't leave him alone".
The girlfriend told police that Belcher said "his child's mother threatened to take all his money and his child if they split up" and "knew exactly how to press his buttons and make him angry".
Belcher shot Perkins multiple times in their home on December 1 and then drove to the team headquarters, where he killed himself in front of his coach and general manager after telling them he "wasn't able to get enough help".
The Jackson County prosecutor's office reviewed the police reports before closing the case on Friday.
It formally ruled the deaths of Belcher (25) and Perkins (22) a murder-suicide, prosecutor's office spokesman Mike Mansur said on Tuesday.
The reports provide new details about the final days and hours leading to the tragedy.
The night before the killings, Belcher went to a club with the woman he was dating while Perkins attended a concert with her friends, the reports said.
Night before shooting
A friend of Perkins has told the Kansas City Star that the couple argued around 1am, about Perkins being out late — although it wasn't clear whether the argument happened in person or on the phone.
The police report, which doesn't mention this dispute, said that after Belcher kissed his girlfriend and she went inside her apartment, he fell asleep in his car.
About two hours later, police roused Belcher after someone called them to report his idling Bentley as suspicious. The report said Belcher was legally parked and didn't smell of alcohol, but officers asked if he could stay inside the apartment for the night.
Belcher tried to call the girlfriend, but she didn't discover the missed calls until the next morning and didn't hear him at her door.
Two women who were up late invited Belcher to wait inside their apartment after he explained his plight. They said Belcher "appeared to be intoxicated" but "seemed to be in good spirits; laughing, joking".
After taking him to a petrol station to buy a sports drink, they gave him a pillow and blanket and he slept on the couch for a couple hours, leaving at 6:45am so he could make it to a team meeting planned for later that morning.
Upon arriving at the home he shared with Perkins, the couple began arguing over "one or both of them going out as in to a club or partying," said Belcher's mother, Cheryl Shepherd, who had moved in with them about two weeks earlier.
Taking his life
When Shepherd heard multiple gunshots, she ran to the bedroom and saw Belcher kneeling next to Perkins' body, saying he was sorry.
After kissing Perkins, his baby daughter and his mother, Belcher drove to Arrowhead Stadium, breaking off his Bentley's rear-view mirror on the way, the police report said.
Chiefs general manager Scott Pioli saw Belcher holding a gun to his head and jumped out of his vehicle so he could find out what was happening.
"I've done a bad thing to my girlfriend already," Belcher told Pioli, according to the report, adding that he wanted to talk with Chiefs coach Romeo Crennel and defensive coordinator Gary Gibbs.
When Crennel arrived, Belcher said, "You know that I've been having some major problems at home and with my girlfriend. I need help! I wasn't able to get enough help. I appreciate everything you all have done for me with trying to help … but it wasn't enough. I have hurt my girl already and I can't go back now."
Belcher asked Pioli and team owner Clark Hunt to take care of his daughter. The Chiefs staff pleaded with Belcher to put down his gun, but he only lowered it to load a round. "You're taking the easy way out!" Crennel told Belcher, according to the report.
As a police officer approached, Belcher knelt behind a vehicle, saying: "Guys, I have to do this … I got to go, can't be here and take care of my daughter." He made the sign of the cross on his chest and fired a bullet into his head, the report said.
Crennel said Belcher had blamed Perkins for missing a team meeting a few weeks earlier, saying he had to watch the baby after Perkins didn't come home the night before.
Crennel said he thought the couple had "trust issues" and Perkins expected "a better life" with an NFL player.
Crennel said Belcher, whose salary this season was more than $1.9-million, "didn't live outside his means". He said he thought Belcher was talking to an attorney about getting custody of his daughter.
Shepherd, Belcher's mother, attributed the couple's relationship problems to "financial issues associated with Perkins' spending habits". – Sapa-AP