Dangers in the Nether: Nether Stalker

A humanoid figure, wrapped in a shawl and with a bow, these hostile mobs are rare in the Nether but if they spot you they will follow you at a safe distance, without attacking you. They have 20 health points and 10 hearts. They are not immune or resistant to lava or fire, giving credence to the idea that they could be from the Overworld, but why are they doing this? Are they Illagers, Zombies, other Players that became crazy, or something else? The shawl and robes they wear hide any possible answers that might lay underneath. Nether Stalkers will flee if you approach them but will always follow you at a safe distance, and have two strategies to take you down. The first is attacking Zombie Pigman next to the player with an arrow. These Zombie Pigman will mistake the player as the aggressor and attack the player but will attack the Nether Stalker if the player leaves/die and the Stalker stays too close. Furthermore, if the player is low on health (3 or fewer hearts), the Stalker will engage in combat, shooting you with arrows, but will flee less effectively during this time, so use it to fight back! This mob will create a sense of fear around Zombie Pigman and while being low on health in the Nether, as the Stalkers can keep sufficient distance between you and them that you don't realize they're pursuing you. This would make Zombie Pigman more dangerous and scary by proxy, even if they don't attack you or you don't see a Stalker(s) stalking you, because there is always a risk that one is stalking you, hidden, waiting for the moment to ruin your day.