I'd recommend taking in any newspapers or mail and leaving a note to tell them that you noticed it piling up and you're holding on to it for them so that their mail doesn't get stolen.
People will look for piled up mail as an indication that it's the right house to break into so it's good community work to help protect someone from that, unless they are an absolutely vile piece of shit who will start a fight with you over this kind gesture (in which case, fuck them.)
I'd also recommend calling in a welfare check asap. They might be in dire need of help. Or worse. It'd suck to know that they didn't get the help they needed and that something could have been done but now it's too late. You've gotta be alive in order to turn a new leaf and sometimes it takes having a broken leg due to an accident and surviving on cat food for weeks (because it's the only food left in the house) with nobody checking on you because nobody cares about you due to you being an insufferable asshole to everyone your entire life before it puts your behavior into sharp contrast and it forces you to change your attitude. I'm not saying that this is a good thing or that it should be considered as a solution but it is what it is.
I'd call it in as soon as possible.