I tell you how it came to it:
McCree basically is a big, easygoing slut. The base knows it. His family knows it. We know it.
He has a big dick and goes commando whenever he can fucking get away with it (and sometimes where he can’t) and loves to feel it swing between his legs and the little glances his teammates sneak him.
He loves jerking it with his door not closed, too.
It’s probably a problem but he kind of hadn’t thought something would ever come off it, y’know? People don’t barge into his small cluttered rooms too often anyway.
So of course Lúcio sticks his head in when Jesse is good and ready to shoot his load, shirt shoved up haphazard, leaving his belly naked because he’s too lazy to do laundry if he gets anything dirty.
And Jesse never actually catches what the kid wanted to tell him (it was asking him whether he wanted some ice cream – bless his lil soul) because he never asked to begin with. Just sat there at his desk with his big, meaty cock in fist and blinked owlishly up at Lúcio who, in turn, just stared.
And maybe you could say that Jesse McCree is a little flattered when Lúcio whispers “Wow” with this absolute awe in his voice as he slips into the room and pushes the door close behind him.
“You like it, partner? Wanna watch up close?” Jesse grins, dragging his hand down to expose the wet head to the cool air of the room and Lúcio’s excited brown eyes.
Lúcio might be a virgin but he was definitely not shy. All enthusiastic smiles and cute dimples as he comes closer and snuggles down on his knees between McCree’s thighs.
It’s basically how McCree ends up taking the pictures of Lúcio carefully, clumsily mouthing at the fat head, pretty pink tongue lapping at the salty fluid.