Oh, AI have had trigger authority for decades. CIWS when armed will engage and fire automatically, but there are also cruise missiles. Whilst those are given engagement areas and sometimes routes/waypoints, once in those areas target identification, classification, prioritisation and engagement are autonomous. The sole difference between a cruise missile operating in this manner and a "killer drone" is there is a more than 0% change to get your drone back again. 'Killer suicide drones' in that sense have been used in anger for decades. The recent sinking of the Moskva with Luch's Neptun is an example: the Neptun will be given a search area within which to find targets (and possibly waypoints to follow beforehand if local air defence is known), but the decision to engage or abort is taken on-board the missile. If there are no targets detected (either due to ECM, or just due to there being nothing there) that's performed without a human in the loop. Likewise, if there are multiple targets (e.g. civilian vessels and a warship) the missile will be performing identification and discrimination without a human in the loop. The venerable Harpoon is rather dumber in this regard, as it's area discrimination is limited to "first thing it sees", but almost any other AShM is more capable.