Both are correct, and I would say equally so. All assassinations are murders by definition, and it is an assassination if the murdered person was murdered primarily because he or she was a public figure like a politician or famous celebrity. Lennon was assassinated because the killer craved the notoriety of murdering a celebrity.
Best wishes - Majikthise. .
Assassination because it sounds cool and because the loonytune who shot him only did so, so he could be famous for doing so. So. Hahaha, look how many times I used that word.