*Minor spoiler request* Was he drugged? My problem early on

I find it really difficult to get invested in & root for a protagonist when the narrative has them doing stupid/reckless things, especially early on. We're just barely getting to know this character and seemingly for no good reason he decides to irresponsibly ignore his sudden extreme drowsiness while driving & careens off the road, getting his sleeping girlfriend killed in the process. Then he follows that up by being vague and evasive with her parents. Not even telling them that she's dead. This is the guy I'm supposed to be rooting for? I know this is a mystery/thriller so is there something later that explains this or is it really as simple as a guy who was too irresponsible to consider pulling over when he got drowsy?