Student or Learner
Do you accept both of them?
He was interrupted twice by some/a troublemaker in the audience.
I accept both.
'...some' can mean unnamed or unknown.
'Some idiot nearly ran me down as I crossed the road.'
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.
**Neither a teacher nor a native speaker.**
Some can be used here, because it's a general statement.
A/An can be misunderstood by someone because it can mean one.
Tonight we will kick some ass.
This doesn't necessarily mean you will kick one ass only.
(I hope it's not too "vulgar", it's a joke )