Can you hit two players with one bullet?
You can not hit more than one player with a single bullet in PU Battlegrounds.
As of Jan 5th 2018 PUBG only has a very limited amount of bullet penetration physics, limited to "doors, water, and wooden shacks" (source).
Bullets, and crossbow bolts, do not pass through other players. In fact bullets will not even pass through the dead body of another player.
So unfortunately, no collateral kills for the foreseeable future.