Clean the exterior of the lock box you have very carefully. Use some throwaway gloves to put your medications and your moms in the lock box, right before you two leave to go somewhere.
Upon return, if the lock box has been moved or broken into, call the POLICE. Tell them what is going on, tell them you want to press charges, and they will check the box for fingerprints. File the complaint.
It will be the CONSEQUENCES of his ACTIONS when he is arrested.
You are not doing him any 'favors' by not reporting it.
J M H O
Love and hugs,