Reporting the freakiest phishing attack ever?

I just got an email from a customer that had a link in it (sendgrid, redirected to something else). The moment it asked for a login, I replied to the customer alerting them that their email has been compromised.

Here's where it gets freaky. The bot replied on that person's behalf assuring me there was no virus. I forwarded that email again to his email ID and the 'bot' that has compromised his account replied again, exactly like a human would, assuring me everything was OK.

Here's the transcript, hoping a some email security folks are around here who can study this further..

------------------

Email moved to pastebin: http://pastebin.com/uXTYCNPu

------------------

Upon which I entered fake auth details and tried opening the link which redirected me to downloading google drive. Called up the customer and turns out (surprise surprise) they didn't send the email.

Now I'm in tech, but this is either a super-freaky AI phishing bot or a really quick human phisher (as I write this up, I realise this could be an option :-|). I'm not sure how effective clicking "Report Phishing" on Gmail is, so posting this here in the hope that someone here can report it to the right folks at Gmail and others so they can detect this in the future...