The mother of Kansas City Chiefs football player Jovan Belcher has told investigators that the argument with girlfriend Kasandra Perkins â€” which preceded his deadly murder-suicide rampage on Dec. 1 â€” was over their 3-month-old baby's paternity, reports The New York Post. Cheryl Shepherd â€” who was in her son's suburban Missouri home the morning he shot Perkins nine times â€” told police investigators that the couple had been arguing over questions that the young girl, Zoey, was even his, said a source close to the situation. "The mother believed that there was an issue over whether [Belcher] was the father," said a source close to the team. "She said he [believed he] wasn't necessarily the father of the child," the source added. A Kansas City law-enforcement source confirmed Shepherd's account of the situation, "She told [police] there was a question about the paternity." Authorities wouldn't jump to conclusions and announce that the baby's paternity led to Belcher's bizarre and violent rampage which left the young couple dead but sheds a little light on what could have set off the NFL player. "But the implication was that [paternity] was what the two of them were fighting about â€” that the baby might not have been his," said a source. Shepherd was visiting her son when the argument broke out early that fatal morning. Â She called 911 after Belcher bolted from the house. Â The Long Island native later shot himself dead in front of stunned Chiefs staff at the team's facility. Earlier in the week, attempts to speak with Shepherd were answered with a, "There will be no comment" on her cellphone. Just a few months earlier, the smiling couple were showing off their new little baby on Facebook.