You saved him from the asylum. Helped him through his trauma, his recovery, and his actions as the the Arkham Knight. You were his rock, his anchor, the one person he felt truly safe around. He'd ask you for advice on everything. His men weren't strong enough? He'd come to you. Nightmares? He'd come to you. And even after years of helping him overcome his past, being there for his darkest moments, this was still a concerning sight.
He's crying, trying to stop himself but not being able to. You knew what happened. He'd confronted Bruce, being faced with so many opportunities to end him but not being able to. He'd revealed his identity, so relieved at finally seeing the man who betrayed him die.
But he couldn't do it, and that was what killed him the most. Jason had spent sleepless nights training and commanding his army, making sure that Gotham would finally be brought to its knees. So much effort, and he couldn't even pull the trigger.
"It's all my fault." He manages to get out between silenced sobs, turning away from you. You'd seem him at his worst, been there through everything, but he was embarrassed of you seeing him like this right now. "All my damn fault.