This attack was done by people who are rather sophisticated. This is not some kind of script kiddie operation. These people have international reach, were able

This attack was done by people who are rather sophisticated. This is not some kind of script kiddie operation. These people have international reach, were able to recruit people to run the ATMs for them, and the ostensible "ring leader" was assassinated. Either organized crime and/or former government agents with cyber security and cyber-spying training.