As investigators search for a motive to help explain why Chiefs linebacker Jovan Belcher killed his girlfriend and then himself, a discordant picture of the couple began to emerge. A friend of Belcher’s girlfriend, 22-year-old Kasandra M. Perkins, said they had lived apart briefly earlier in the year but had gotten back together by Thanksgiving. Brianne (Bree-ahn-eh) York said Sunday the couple argued about “normal couple stuff” but that her friend was “really happy about being a mom.” York thought there was some mistake when she learned Belcher had killed Perkins at the couple’s home Saturday. Police said Belcher then drove to Arrowhead Stadium, where he thanked his coach and fatally shot himself. Belcher and Perkins had a 3-month-old daughter, Zoey.