iPhone went to black screen on won't turn on

iPhone 7+ suddenly black screened then the loading rotating thing appeared. Few seconds later it shut down and now won't turn on. I tried to connect it to my pc and an iTunes message popped up saying that iPhone is in recovery mode and can only be used after restoring. Also tried to press the lock button with the volume down button to no avail. PLEASE HELP! We have heaps of photos we need to retrieve.