Yes, working alone. He was filling in a crack by a house and then trying to press the earth down and the crack opened up again it seems. There were no eyewitnesses so it's not completely certain what happened.
I hope for a miracle but I think he must be dead, I'm not sure how he could have survived. It's horrible. They are continuing to search. They have lowered people down in a cage thing and are digging earth out of the crack, but no results so far.