Michael Ealy as Justin...what's the backstory?

Am I just so far out of the loop? But why do they keep mentioning him in Atlanta and getting her fired? I thought Ealy came in this season, perhaps I forgot because it took them over a year to come back on the air and well not only was that careless but people can forget shows in that amount of time. So tell me, what did Ealy's character do to get Mary Jane fired, I thought her behavior was what got her fired.