Snape had just briefed Dumbledore about the results of Pettigrew's interrogation, when it struck him that in all the bustle, it was quite likely no-one had told Al yet about what had happened his friend.
Better me than Moody or some Auror.
He Apparated to the research lab, then when he found that was empty he tried the next most likely place, the Owlery.
"Ah, there you are." He studied Al's expression, trying to determine whether anyone else had told Al the bad news.