Samsung Galaxy S3 Dead . . .

[AC Question]

I have an old Samsung Galaxy S3 phone, and I was planning on flashing a custom ROM. I rooted it successfully with KingoRoot, then installed ROM Manager from the Play Store. I flashed ClockworkMod from the ROM Manager, then accidentally pressed "reboot into recovery". The phone rebooted into a screen with the phone saying that the custom recovery can be harmful and all, because I forgot to unlock the bootloader. So I pressed Volume Down and Power at the same time to restart into the phone. Then I install EZ-Unlock to unlock my bootloader. I think it was successful, but when I turned off the phone, I couldn't turn it on again. No boot screen or anything. I tried putting in the charger with the battery in, but nothing. Then I removed the battery and put the charger back inside, then an orange notification light appeared for 1-2 min, then disappeared. I don't exactly know what happened.

I tried the debrick process for the Samsung Galaxy S3 from XDA, but nothing happened. I really don't know what to do and would appreciate any help. Thank you in advance.

 

[smvim]

In the future I'd recommend to avoid Kingo, you have an older Samsung device so there are much safer and more private rooting solutions available. You can use either the Odin utility (requires Windows PC) or Heimdall (available for Linux, Mac, and Windows) to root your S3.
But getting back to your current situation, if you can't even boot your phone up into its Download Mode (simultaneously holding down the Power, Volume Down, and Home buttons) then try pulling the battery again but this time leave it out for few minutes. Then put the battery in and try to boot your S3 again. If it's still dead, you might want to try using a jig. A jig is just a little device that you plug into the USB charging port. You can make one yourself:
https://www.xda-developers.com/need-a-samsung-usb-jig-build-your-own/
or they only cost a few bucks on online retailers like Amazon.
Hopefully with your phone bootable again, if it starts up you can work from there. If it just starts up into either its Recovery or Download Modes, you should think about flashing a stock ROM and return it back to its original Android OS, and then root it. Both the sammobile and updato sites are reliable sources for Samsung stock ROMs, be absolutely sure you download the ROM that exactly matches your S3 model, there are no mix-and-match ROMs that can be substituted on a whim, you have to use the one that's specific to your model.
sammobile
https://www.sammobile.com/firmwares/search/galaxy s III/
updato
Download Firmware – Samsung Update
Here's a guide on how to root your S3:
How to Root Galaxy S3 on Android 4.3/4.4.2! [NEW] | GalaxyS3Root.com
Note that the article is dated, the process is still valid (as the S3 is also quite dated, and Samsung and the carriers stopped supporting years ago) but some things have of course changed since then. As far as Recovery images both CWM and Philz are no longer actively supported so you might want to to opt to use TWRP (although if you do choose CWM or Philz they will both still work out OK).
https://twrp.me/devices/
Regarding Odin, there newer versions but there's not a lot of backwards or forwards compatibility so use the version stated in the article or use the recommended version (3.09) from here:
Download Odin (All Versions) for Samsung Galaxy Devices
If you don't have access to a Windows computer (to use Odin) than take a look at Heimdall, an Open Source equivalent to Odin:
http://glassechidna.com.au/heimdall/