He was already fired when he "leaked" it. Also, let's be very clear about "leak." Did he print the memo and mail it? FWD it to his gmail then send it to his friend? Read it aloud over the phone? Or did he call him up and give him the gist? Do you know enough about the ownership of "government property" to say which of these, if any, is more illegal/terminable than the others?
If he was already fired when he "leaked" it, then presumably he wouldn't have access to the original copy unless he duplicated it.
I think it stands to reason that he shared the content of the memo based on his own recollection. Which--if you listen to the full interview with the guy to whom he "leaked"--sounds as if it's the case. As if he was "given" the content from Comey in a very conversational way. As one would between friends.
So...again.
About that "leak?"