(Reuters) - Kansas City Chiefs linebacker Jovan Belcher shot and killed his girlfriend - and later himself - after he spent the previous night in an entertainment district and slept at the apartment of another woman, witnesses told police.

The events could explain why Belcher got into an argument with Kasandra Perkins, the mother of their 3-month-old child, that preceded the murder-suicide.

Five hours before he shot Perkins, Belcher was questioned by police when he was reported sleeping in a car outside the other woman's apartment, police said Tuesday.

Police responded to a suspicious vehicle call about 2:50 a.m at an apartment complex near downtown Kansas City, Missouri, where they found Belcher dozing in the car, Sergeant Darin Snapp said.

Officers woke him up and asked what he was doing, Snapp said.

Belcher said he was waiting for his girlfriend to come home and didn't have the door code number so he could not go inside, Snapp said. Belcher then called someone on his cell phone and about that time a woman came to the door of the apartment and waved him in, Snapp said.

Belcher had been partying in an area of bars known as the Power & Light District, police said, and later went to the other woman's apartment.

After finding him in his car, police ran a report on Belcher, 25, and after looking at his driver's license found nothing noteworthy and had no reason to hold him, Snapp said.

"He was very cooperative and did not give us any problems," Snapp said. Officers did not see any weapons, Snapp said.

Witnesses who live in the apartment told police later that Belcher went to sleep there and at his request they woke him up at 6:30 a.m. so he could get to a Chiefs' team meeting by 9:30 a.m, Snapp said.

Belcher returned to his home in Kansas City he shared with Perkins, 22, and the couple's 3-month-old daughter, police have said. The couple got into an argument and at 7:50 a.m. police responded to a call from the house and found Perkins shot dead in the master bedroom.

Belcher's mother was at the house at the time of the shooting. After the shooting, Belcher kissed his wounded girlfriend on the forehead, kissed his daughter and apologized to his mother, according to the Kansas City Star, details that Snapp confirmed.

Belcher fled in his car to the practice facility, where he encountered Chiefs' General Manager Scott Pioli and other Chiefs' staff in the parking lot, police have said.

Belcher then stepped out of his car with a handgun pointed at his head and said, "I did it, I killed her," Snapp said.

Pioli tried to persuade Belcher to drop the weapon. Head coach Romeo Crennel arrived on the scene and also tried to talk Belcher out of hurting himself, police said.

"Guys, I have to do this," Belcher said, according to the Kansas City Star, citing multiple police sources. Belcher ducked behind his car, made the sign of the cross and fired a shot into his head, Snapp confirmed.

On Monday, Chiefs Coach Romeo Crennel said he tried to talk Belcher out of shooting himself outside the team's practice facility before the player committed suicide.