It's thought that the pineal gland releases a massive amount of DMT during dying which explains to some extent the "tunnel of light" type visions people report after near-death experiences. As someone who has done DMT and experienced a rare endogenous DMT experience during REM sleep, I have no doubt that the phenomena mentioned in this article is a result of a large dose of DMT easing the transition into death. It needs to be studied a lot more than it has.