Connor could be faking it. That's entirely possible.
But on the other hand, this is just an extreme version of how he freaks out. And full disclosure laughter is always for some reason how I respond to terror/ grief/ shock before another symptom kicks in.
From wikipedia: Unhealthy or "nervous" laughter comes from the throat. This nervous laughter is not true laughter, but an expression of tension and anxiety. Instead of relaxing a person, nervous laughter tightens them up even further.
Still hate Gabriel but boy that actor can cry. His mom needs to go though.