After you see the triangle
Hit both volume buttons. A menu should come up, try to wipe everything then factory reset. The boot loader shouldn't have a triangle. When you boot the phone you should be holding the camera and volume down buttons press power while holding both and release. You should see a black screen asking for a connection. If neither of these work I think you are SOL. The only other idea I would have is to order a new battery and charge it up full and try again.