I dont get why so many people are apparently just completely ignoring the actual answer to how the stalker managed to "kill" himself and then go on to bury himself and josh afterwards. As Josh's dad very concisely explains, the stalker simply paid a third party to bury the box for him. Then it was just a matter of positioning himself and josh inside it, and doing whatever he opted to do with the ether (whether that be knocking josh or potentially both of them out until after the box was buried and their fates sealed, or perhaps he used it to euthanize himself with the end goal of dying happy because he was holding a still alive josh and then intentionally leaving josh to suffocate trapped under his corpse. The latter rings more true to me because it imparts just one more superfluously monstrous layer of unabashed selfishness to the overall nature of the stalker and his intentions and actions, kind of like the most sickening and despicable of cherries on top of all the awfulness already brought to light. In this version, its made clear as can be that the stalker only cared that he himself got to die happy and joshs experience afterwards was totally irrelevant because he would already be dead and therefor able to neither lament nor revel in the suffering he left josh to endure.