The Sept. 6 missile strike on Kostiantynivka in eastern Ukraine was one of the deadliest in the country in months, killing at least 15 civilians and injuring more than 30 others. The weapon’s payload of metal fragments struck a market, piercing windows and walls and wounding some victims beyond recognition.

Less than two hours later, President Volodymyr Zelensky blamed Russian “terrorists” for the attack, and many media outlets followed suit.

But evidence collected and analyzed by The New York Times, including missile fragments, satellite imagery, witness accounts and social media posts, strongly suggests the catastrophic strike was the result of an errant Ukrainian air defense missile fired by a Buk launch system.

Ukrainian authorities initially tried to prevent journalists with The Times from accessing the missile debris and impact area in the strike’s immediate aftermath. But the reporters were eventually able to get to the scene, interview witnesses and collect remnants of the weapon used.