Q: Black screen with no response, only iTunes recognizes my phone is connected

Hi, I have an iPhone 6 Plus and I clicked the sleep button to check the time and my screen went blank and then went black. I tried many times to do a hard reset, but there was no change, along with keeping it connected to the charger for 2 hours and still no response. I then connected it to my computer and iTunes recognized it was connected, but gave me the message that there's a passcode on my phone and will not be able to go any further with the normal backup procedures until the passcode is entered. So I have no idea what to do as I am a college student with a phone that is only a year and some months old with no damage to it. Please help, anything would be appreciated!