Since you adopted him, do you


Since you adopted him, do you know his background at all?  Shock Collars and such devices don’t teach them what they are doing is wrong, they just don’t do it because of the end result. He may not grab onto other dogs anymore, but maybe something else?  How much obdience training has he had?  How much has he been socialized?  Those two things, are probably the biggest in keeping his aggression at bay.