Received a strange message from unknown person

So earlier today I received a notification of a new conversation started on WhatsApp. I click the notification and it opens a new WhatsApp chat.

The person who started the chat didn't say anything so I wrote the first message saying 'Who is this'.

They replied with two messages. The first said: *Person's name* has shared a publication, and a link to a Facebook group. The second message just said 'Your worst nightmare'.

I click the link and it takes me to a Facebook page where it says sorry but the link was removed or broken.

A Google search of the number didn't bring up anything helpful about who this was.

I just blocked the number and deleted the chat and the archive of the chat.

What the hell? Has anyone had anything similar happen to them?