lololololol. When the speaker is very angry or shocked, not believing what happaned or is going on.
I just found it very cute: Probably a he huh? He uses another f word instead of that f, to express his extremely strong shocked feeling that normally requires that f to work with the structure, awkward like saying "un-really-believable", see what I mean? To be as polite as 'reakin', you can also say 'riggin', another f bomb.
Theoretically it'll be all tenable to put words in the order: Prefix - adverb - adjective (usually the "-ble" ones) And it looks like the one you brought up is the most popular one. Same as: abverb prefix-adj It's f...ing unbelievable...