Since he spent some time in what he thought was his furever home then found himself back at the shelter, poor Schroeder might feel unsure of his new situation and afraid he might be sent back to the shelter again. It will take some love, patience, and time to reassure him that he's with you to stay. Like all kitties, Schroeder just wants to be loved and cared for but his recent experiences make him uncertain. Give him lots of attention, tell him how wonderful he is, and give him lovies on his terms for now. Follow Schroeder's pace and reassure him. This will work out.