Is a sentence like 彼がやったんだ past or present tense?

Question

For example, in an a situation like

誰がやった？

彼がやったんだ

Would the latter sentence be considered past or present tense? Is んだ a combination of の and だ with だ as a copula, or is it a different word altogether that functions more like other sentence ending particles like よ,ぞ,な, etc.

Answer 1

Both is past tense. The former is a question the latter is an answer (he did it).

This topic is similar to this question: のだから vs のだ (んだから vs んだ）