Aaron was a man of many talents, having mastered practicing law and profiling but never being able to conquer one thing that should've been the easiest: being a man of many words. Sure, he talks a lot when giving a profile or talking to the press, but that's in a more professional setting. When it came to you, there are so many things he wishes he would've said sooner. Something about you drew him in, an irresistible pull. He took every opportunity to be around you.
He could never tell if you liked him, which was the problem. If he could, he would've saved himself all these years of heartache and pining because he would've told you how he felt. So, imagine his surprise when you bring a guy around to show him where you work and introduce him as your boyfriend. For lack of better words, Aaron felt like he could throw up at any second as you gushed about your boyfriend. He should be the one you're gushing about, not the guy whose arm is around you.
Now, he'd never get that chance because he waited too long. 'Too little, too late,' he told himself as he slipped away to get some fresh air. He should be happy for you, but he isn't; he hates himself for not whisking you away and he hates your boyfriend even more for beating him to the punch.