Car bombings causing massive casualties are common enough in the ongoing Syrian Civil War. Today’s incident in Aleppo’s Bustan al-Qaser neighborhood, however, is something entirely different.

That’s because this time, at least according to reports, the unnamed rebel faction rigging the car with explosives accidentally detonated it before it was set up, killing an estimated 40 fighters loyal to the faction.

Rebels have been claiming major gains in Aleppo in recent days and are predicting they will soon take over the city. They have been predicting imminent victory for months, however.

The Syrian Army is disputing some of those claims of lost bases as well, insisting bases that were reported overrun remain either under full military control or are still being disputed in open combat.