I would take that as a direct greeting being professional on the stern side. I know that I greet most through my e-mails with an informal “Hey, name” or “Hello, name” to ensure I am friendly and approachable. But when I want to have a more direct tone, I skip the Hey or Hello. Maybe that’s the case here — maybe not. If you are unsure of the Sender’s intent it is best you call or meet in person, if possible, to discuss and avoid any possible misunderstandings.

One thing I would refrain from repeating in the future is to not Cc: others in an ongoing conversation with another individual. They were communicating with you, not the others you chose to bring into the conversation. I just posted about this very topic here: Who Should You To: or Cc:?

HTH!