If you interview someone and don't even send an email to let them know they're going in a different direction, you're a . I interviewed SO many times for my first teaching position and it is exhausting the waiting, waiting, waiting until it just sort of wears off.
If it's an INTERNAL hire, you absolutely need to give that person a call or meet in person. Administrators can be such cowards about delivering bad news. I'm sorry that happened.
At the very least it's a good lesson for what you won't do when you pull in this job on Monday