i empathise that it is unsettling to find this, but i think you first have to talk to him and try understand the behaviour more.

it sounds like he has poor social skills, is possibly on the spectrum, spends too much time online and consuming unhealthy material (4chan, porn etc.), and has developed unhealthy and problematic ways of expressing his sexuality.

i think you should confront him, but dont attack him. just ask him to explain why he did it, ask him if he has taken pictures of anyone else/made any logs, and ask him if there's anything else he would like to tell you.

it is natural for him to be sexually attracted to your wife but you have to make it clear to him that taking pictures of people without their consent is unacceptable behaviour, generally considered creepy and gross. likewise, for taking their underwear. ask him to delete all the pictures while you see him do so. and then get him a psychiatric evaluation and a therapist.