The US investigated an attack in Syria that killed and wounded civilians, and concluded that no specific person was to blame. That could be a falsehood to protect the guilty. But not necessarily: it could be true. If so, there are two possibilities:

1. The system for making decisions was at fault. If so, the US has an obligation to correct it.
2. It's one of the deadly accidents that tend to happen in war and can't always be prevented.

No system can prevent all the unnecessary killings in war. But officials are often too quick to conclude that any given killing was nobody's fault and impossible to prevent.