How do you unbrick a hard bricked samsung galaxy s3 using computer and usb cord

[AC Question]

Recently i bought a samsuung galaxy s3 off of the internet and when it arrived i checked to see if everything was good. when i took the back off the sd card and sim card reader were broken off. so i turned the device on and it worked perfectly. started to root the device and when i tried to download supersu binary a notification popped up and said "knox is installed on this device,this can cause root access to be limited. would you like to remove knox?" when i did that the phone tried to reboot and then it was hard bricked. the only thing that works is when i plug it into a computer without the battery inserted via usb cord and the charging light appears then my computer tries to install the driver for it. after about 20 seconds the light turns off and my phone disconnects with my computer. Is there anyway to unbrick it by using a computer and usb cord? please help