I haven't seen the earnings release yet but at 4:02 EDT I saw after hours quotes at $10 and change.
How can you even process earnings info in 2 minutes, assuming it was released the second after the market closed?
Not to mention there was no earnings warning in advance.
My theory, until I see more evidence: PEGA is thinly traded and it doesn't take much to send it down, especially after hours. In fact it is usually down AH on most days. Could be that after a big down day for the market a few traders knee jerked it and shorted it AH. I dunno. Let's wait for the numbers.