Jailbroken iPhone 4S after factory reset doesn't load
Yesterday I attempted to factory reset my jailbroken iPhone 4S (iOS 8.3) using the option in settings. At that point, I didn't knew you shouldn't use this if you're jailbroken. After the operation, phone displayed the Apple logo and didn't want to load.
I googled the problem and decided to try recovery mode. Phone shows "connect to iTunes" screen and once I connect it, iTunes detects phone in recovery mode and asks me to choose between updating or restoring the device. No matter which one I pick, error code (-1) comes up right at the end of the process.
I tried DFU mode, same result.
I tried downloading iOS 8.4 .ipsw file and installing it using shift + restore, same result.
I have also tried exiting recovery mode with Reiboot (couldn't find a way to do this with tinyumbrella), it worked, but once I turn the phone on it displays apple logo for a while and then shuts down.
Phone is currently back in recovery mode and I have absolutely no idea what to do next, having spent last few hours googling the problem and trying solutions other people posted. Please help me.