In an interview Rothenberg said that their will be a musical act. And Marie Avgeropolous said "Yea, for three seconds". So I think his character will get into debt, and he has to repay a gang or something but he doesnt have enough money, so he starts to sing for them, and then three seconds in the gang leader gets annoyed and shoots him and kills him. Thats my theory.
Good theory. I'm gonna add onto it a bit. Maybe instead of an actual gang , there's a small group of exiled and/or rogue Grounders he encounters? Like you said, maybe he tries to sing for them but is end up killed instead.