How are you today? It does sound like this was a massive cry for help rather than an actual suicide attempt, but whatever it was, you are not to blame.
I lost my fiance through suicide several years ago and although I knew he was depressed and he had threatened to kill himself many times, I didn't think that he would ever go through with it. Looking back now, with the benefit of over 25 years and hindsight, it was inevitable - but we are not blessed with that wisdom when we're going through the situation.
People don't always announce their intentions and you cannot possibly have known what was going on in his mind. I know of cases where the partner of someone who killed themselves didn't even know they were depressed - they came home to find them dead, or learnt that they had died when the Police came to the door.
I have also learnt that when people are really determined to kill themselves, they make sure that there is no way that they can be saved - they take massive ODs, they stand in front of a train etc.
Only he knows what he was feeling yesterday and only he knows how he is feeling today. I know that it is hard to see the positives in this situation for you at the moment - but look at it this way: you know he is stressed and depressed and can help him, he will receive treatment/counselling from mental health professionals who will work with him to resolve his suicidal feelings. It is a long, tough road ahead, but there is a light at the end of the tunnel. He is alive.
Hope that this post hasn't upset you - my only intention was to bring you some sort of comfort.
Look after yourselves and all my very best wishes.