We crossed the line of machines that automatically kill a long time ago. A heat seeking missile, or a shell that detects and target tanks [1] are effectively doing that. Software selects the target. The soldier only points in the general direction. AI is only a small technical increment.
It's never really that clear-cut, though. Human drone operators, pilots, etc. routinely send missiles into cars, buildings, weddings, etc. that cause collateral damage, killing or maiming innocents and passers-by. Sometimes it's an accident, but not always.
And that's just when we even try to limit damage, vs indiscriminately firebombing or nuking entire cities.
We shouldn't demand perfect accuracy of AI when we don't expect the same of humans. Long ago, we decided collateral damage in war is acceptable, especially when you end up winning the war and there's nobody left to prosecute you except historians =/
[1] https://en.wikipedia.org/wiki/SMArt_155