ATT Galaxy S3 Root Failed, won't boot up. No command
So I recently got the Galaxy S5 and decided to root my old Galaxy S3. It's ATT, and runnign 4.3. The root failed, I had to pull batter because of loop. It now won't boot fully into the Android OS. I plug it into a charger, and the battery symbol comes up for a second. Then dissapears. Then comes back, so on and so forth forever. *Sometimes* I can get it to boot into recover. It shows a dead android, red triangle, and says something about 'No command' and then turns off. I think I may have tripped Knox. Is there any way to recover this phone?