So long as he didn’t trespass or attempt to do so (eg attempt to get into Malloy’s vehicle), why shouldn’t he have followed Malloy? Is it a crime to follow someone? I’m not sure that it’s even harassment if someone shouts questions at another person in a public area, even if the person being questioned has asked for the questioner to stop. Malloy was certainly well within his rights to ignore the questions and walk away, but the student did nothing wrong here (unless there’s more to the story, of course).
But following someone around is a good way to draw harassment and/or stalking charges.
Especially when that person is an elected official, where you could be suspected of tracking his movements to find out where his security is most vulnerable.