A planned prisoner exchange went disastrously wrong Wednesday when a Russian military plane crashed in the Belgorod region, killing more than 70 passengers, almost all of whom were Ukrainian captives, according to Russia.

The Kremlin claimed Ukraine shot the plane down with surface-to-air missiles fired from besieged Kharkiv, where casualties attributed to Russian airstrikes number more than a dozen over the past week.

Ukraine didn’t immediately deny the allegations, pointing instead to the Russian bombardment and efforts to “destroy” the “delivery vehicles” facilitating it. In other words, Kyiv considers Russian military transport aircraft to be legitimate targets when they’re flying near the border, as this one was.

There was some indication that Ukraine thought Russia was moving S-300 missiles on the plane. “The recorded intensity of the shelling is directly related to the increase in the number of military transport aircraft that have recently been heading to the Belgorod airfield,” a statement attributed to the General Staff of Ukraine’s armed forces read.

As to whether mistakes might’ve been made Wednesday, there was no immediate word, but Ukraine did confirm that a prisoner swap was on the calendar. Moscow said Kyiv was “well aware” that the captives were being transported in a military plane “in accordance with established practice.”

Belgorod, you may recall, was the site of the deadliest Ukrainian attack on Russian soil of the entire war last month, when Kyiv retaliated for a brutal aerial barrage in which Vladimir Putin deployed “nearly every type of weapon in [Russia’s] arsenal,” as Volodymyr Zelensky put it at the time.

Videos (or a video, anyway) of Wednesday’s crash circulated widely on social media. It wasn’t pretty. There was no way to verify Russia’s initial claims regarding the cause of the incident, but it’s safe (or unsafe, depending on how you want to look at it) to say everyone on board was definitively killed. The plane appeared to fly straight into the ground in the town of Yablonovo, where an onlooker captured a dramatic explosion.

Subsequently, Ukraine’s military intelligence apparatus seemed to acknowledge the possibility that it inadvertently killed its own POWs. Russia, Ukraine said, was supposed to “ensure the safety” of soldiers being transported “under the agreements that had been reached.” Ukraine wasn’t notified of the need to safeguard the relevant airspace “at the defined time.” The statement went on to fault Russia for “deliberate actions aimed at putting the lives and safety of the POWs under threat.”

Earlier this month, the two sides swapped hundreds of prisoners in what counted as the biggest exchange of the war. According to the Media Initiative for Human Rights, a journalist-run Ukrainian NGO cited by The New York Times, former Ukrainian prisoners freed in previous swaps said they were indeed flown on IL-76 planes like the one that crashed in Yablonovo on Wednesday. A Russian lawmaker said another IL-76 carrying dozens more prisoners turned around before it could be targeted.

As the Times noted in the above-linked article, Ukraine is increasingly resorting to “long-range strikes with drones and sabotage operations inside Russia” amid a bloody, arduous stalemate along the front lines.

Additional US aid for the war effort is tied up in Congress. Until the logjam on Capitol Hill breaks, the Pentagon is out of money for Zelensky. Earlier this week, Lloyd Austin exhorted a group of 50 nations to “dig deep to provide Ukraine with more lifesaving ground-based air defense systems and interceptors.” He spoke via video conference from his home, where he’s recovering from a highly publicized hospitalization.

On Tuesday, the Kremlin unleashed a punishing barrage against Kharkiv, where half a dozen people were killed and nearly 60 wounded when a combination of S-300s, Kh-32s and Iskanders tore into some 30 residential buildings.

Whether or not a definitive account of Wednesday’s tragedy in Yablonovo emerges, the overarching takeaway is the same as it ever was: War is hell. And yet, as a species, we can’t seem to stop engaging in it.

Asked Wednesday if The White House had any additional information on the incident, John Kirby said, “No, we don’t.”