Article continues below advertisementA source claimed Justin Bieber and Usher's recent spat at Beyoncé and Jay-Z's post-Oscars party on March 15 was a long time coming."This didn't start that night. It's been simmering for a long time," one insider said of the incident, which another source described as a "heated exchange" that started with Usher coming up to the father-of-one with "energy and anger.