The house is empty because YOU aren't there. Whatever you left - he's not noticing it. He's dismissing it. He wants you all back, he wants everything back the way it was and will do what it takes (short of actually taking any responsibility) to get it.
He's on suicide WATCH, so he hasn't actually done anything serious, only indicated the likelihood.
I've taken a friend to hospital under similar circumstances, we were actually on the way home from seeing her psychiatrist and the hospital was right on the way. As we got closer to the hospital, she became more bizarre; I think she felt the consultation with hr shrink had not properly addressed her concerns, and she wanted more, so she asked me to take her to emergency and I watched and listened while she talked her way into being admitted. She made it fairly clear that she did not feel safe going home, she needed to be admitted for her own safety. But all that drive to the hospital - she at no time seemed to be out of control, she was holding herself together.
Picture this. He's managed to get himself admitted to hospital. Who knows how, there are many ways. It's really easy to say to someone (like a family member). "I feel really lonely, really depressed. I can't go on, the house is so empty. She's taken everything, I have nothing to remember them all by. Poor me, poor me, woe is me, I can't go on."
First you say it to a drinking buddy. Then you say it to family. It scores a lot of sympathy. You feel vindicated, justified in feeling miserable. So you say it to more people, as long as they take you seriously. ("oh, no, don't do anything rash, what would we do without you? You need to get help, you can't let yourself get down about this, you've been through so much, you must ask for help...")
Eventually this snowballs, with him getting ego stroked all the way, until he gets admitted to hospital - the ultimate attention-getter. "Wow, I'm so miserable that they think I might hurt myself. Meanwhile, I've got a bed I can sleep in and round the clock women waiting on me ,watching over me to keep me safe. 'Four angles round my bed...' and all for me. If only my missus could realise that THESE people value me..."
And of course, part of this fantasy he build up in his head is the lovely image of his sister sobbing down the phone to you about what you've done to him, you feeling all remorseful and rushing to the hospital pleading with him to not do anything foolish, you made a mistake, all is forgiven, let's set up house together again and live happily ever after.
None of this has any connection in his head, to WHY you left or what he will do to try to fix things. he just wants the broken toy made fixed again with no sign of a break, all kissed better and BACK TO WHERE IT WAS.
Don't do it. or if you really have changed your mind, make sure it is for rational reasons and not purely the emotion of the moment, or you will be even worse off than before.
Marg