撃つんだ

I'm going to shoot

→ 撃つ

phrase Uncommon #12,666

I'm going to shoot んだ adds an explanatory or emphatic tone. The exact meaning depends on context; it can also sound like a command, such as “Shoot!”

JA: 今だ、撃つんだ！

EN: Now! Shoot!

Why are you shooting a gun?

— グエムル -漢江の怪物- (2006)

Shoot him in the legs so he can't run.

— グエムル -漢江の怪物- (2006)

Why are you shooting?

— タクシー運転手約束は海を越えて (2017)

Why are you shooting?

— タクシー運転手約束は海を越えて (2017)

Shoot!

— グエムル -漢江の怪物- (2006)

Anyone who doesn't say the password gets shot.

— 炎628 (1985)