Shadow Tactics: Blades of the Shogun

The earliest this can be earned is during the eighth mission, but it can also be unlocked during the 13th mission.

At the beginning of the eighth mission, when you're still outside Kanazawa castle, you will be in a warzone. Simply shoot any enemy here and the trophy will unlock, although for the purposes of the mission I would recommend shooting an enemy officer.
The thirteenth mission also has two shooting ranges where this can be earned, one near the beginning of the mission and the other near the end.