Jack sighs, and nods, looking more exhausted than anything. He leans back against a railing and folds his arms, clearly turning over the events of the last few days in his mind.

"Well, he did try to kill me."

He hears the warning in Genji's voice and elects to ignore it--instead speaking as neutrally as possible, just presenting the facts.

"And I'm not sure when he started planning it."

Implying, of course, that it's not going to be so easy for Jack to accept this, because Gabriel could have been having mutinous thoughts in the years leading up to the attack on HQ. Jack doesn't sound accusatory--just a little sad. He knows that former Blackwatch agents might have more insight into Gabriel's machinations towards the end than he ever did, or could hope to have, so maybe he's just hoping Genji will tell him what he knows, if anything.