THEORY

Ok from my guess, I think what happened was that Soohoo was supposed to die when he was young and the one who was supposed to take his soul was Taker. But as we can see from the flashbacks and his mindset about humans, he wouldn't want to.

So there's two possibilities right now and that is either, Taker destroyed his 'book of life'(the blacklist) so he wouldn't have to take Sohoo's soul.

OR he made a deal with his mom to destroy his 'book of life' and instead put her own name on another angel's blacklist and disguise it as an 'accident' involving a 'human' so it wouldn't look so suspicious to the higher ups/chief.