Help, can't boot into Recovery, TWRP failed, No ROM, MAC

view story

http://forum.xda-developers.com – HELP! i can't boot into recovery! i was wiping data to flash another rom, and TWRP quit on me. so no rom on it. only will go to the boot screen twrp fails. whenever I try to go into recovery, it stops at the TWRP logo and turn back off. I can't get into any TWRP menus, etc. then goes to the Samsung screen, w/ "booped by BMS" but freezes there. i don't have a PC, so i can't push something to it through ODIN. what can i do? can i use CASUAL? somehow? I have a MAC. Verizon Galaxy s3. Can Casual push a rom onto it? I read that i can use ADB, but I need to b (HowTos)