I'm going out on a limb with this - and note that this in no way represents anything but my own, personal opinion - but today's airstrike that killed 62 and injured 100 Syrian soldiers outside of Deir ez-Zor was not an accident. Here's why.
First, the US-led "international coalition" has not previously operated in this area. Though the city is under siege by Islamic State (ISIS), it's an enclave held by the Syrian Arab Army (aka "Assad regime forces" for you mainstream media viewers). There are no US-backed "moderate rebels" anywhere near.
Secondly, the US reaction. The official line is that this was "unintentional." I may have bought that if the strike was conducted solely by F-16s flying at a high altitude, but A-10s are ground-attack planes that can get in low and close. They should have known they were striking a Syrian Army base - especially if they had intelligence on the area, which they say they did.
Now, note the Central Command statement on the incident:
“Syria is a complex situation with various military forces and militias in close proximity, but [the] coalition would not intentionally strike a known Syrian military unit.”
Not only does the excuse not apply to this particular area, but "would not" does not mean "did not."