Theo watched the man crumble to the floor, sobbing and staring ahead of him, seeing something that was not there. It did not take more than a look to see that the exercise had broken him, turned him irreversibly mad. It was a well known side effect to tampering with people's memories.
To Theo it mattered not at all, the man was of no use to him any longer and he could decide later whether to kill him or obliviate him and send him to a Muggle asylum where he'd never be found. He would contact the Dark Lord, see what kind of evidence he wanted before committing to any piece of action.
Taking Snape's hand immediately, he Apparated them back to the library where a Pensive was brought within seconds.
Theo gestured towards the basin. "Go right ahead," he said simply, sitting down in the sofa and waiting for Snape to get ready.