my iPhone is black and won't open

I used assistive access and it took a while to start by mistake I closed the screen and now it turned black, and when i pressed 3 times on the power bottom it did vibrate and i thought it's about to open but then a warning voice appeared (so basically the phone glitched and it's locked and i'm not too sure if it's software crash or hardware issue (the iphone is charged about 70/60%)) .

i need assistance asap.

thank you