The hook killer was probably inspired by one of many urban legends surrounding the dangers of Lovers' Lane.
Made worse in the third movie, since he becomes a ghost or zombie (it's not clear). So now there is virtually no stopping him.
The accident comes completely out of nowhere. The four teens are enjoying their night, and the man just wanders out into the middle of the road. Ray was distracted for a moment and that's all it took. They first assume it was a deer, but Julie is already panicking - "if it was a deer then where is it!" - and then they find the boot.
Barry is pretty unnerving during the whole ordeal. He's drunk sure, but you wonder how violent would he have gotten to the others if they hadn't gone along with the plan? He looks like he's ready to strangle Julie when she initially refuses.
Max's sudden death. At first you don't know what the deal with the note is. Seeing him getting hooked in the throat tells you that this is what awaits the teens.
The killer easily snuck into Helen's house, past her father and sister and hid in her room without her even noticing. Helen waking up to find some of her hair on the pillow...she suddenly knows that something must have happened.
Julie finds Max's body in her trunk. And a more mundane fear - but the shock nearly makes her stumble into traffic. Then there's the body being moved before she got back to the car - Ben Willis was waiting for her the entire time!
The entirety of Helen's chase, which goes on for a long time and tortures the poor girl several times before the killer finally gets to her. She has to escape from a police car and run all the way to the store, where Elsa is clearly apathetic to her screaming and takes her sweet time to open the door. Then she has to run through an alleyway but the marching band's noise prevents anyone from hearing her call for help.
Elsa's death too. She turns around to see someone standing in front of her holding a hook. She knows what's about to happen to her and all she can do is scream as he raises the hook.