Russian military commander Vadim Shishimarin, accused of killing a Ukrainian civilian in the Sumy region on Feb. 28, is set to go to trial on May 19, according to Ukraine's prosecutor general Iryna Venediktova.

The 21-year-old soldier allegedly fired his AK-47 at a car driven by a 62-year-old Ukrainian man, killing him at the scene, Venediktova said.

Shishmarin is charged with murder and two counts of robbery.

Prosecutor Andriy Syniuk said Shishmarin has cooperated throughout the investigation.

He is the first member of the Russian military to face charges, Venediktova said.

He could face a life sentence if convicted.

-ABC News' Nadine El-Bawab and Tatiana Rymarenko

On a Friday phone call with Swedish Prime Minister Magdalena Andersson and Finnish President Sauli Niinistö, President Joe Biden "underscored his support for NATO’s Open Door policy and for the right of Finland and Sweden to decide their own future, foreign policy, and security arrangements," according to the White House.

White House press secretary Jen Psaki said Thursday that the U.S. "would support" Finland and Sweden applying to join NATO "should they choose to apply."

Dmitry Polyanskiy, Russian deputy ambassador to the United Nations, told a British news podcast that Finland and Sweden officials "know the moment they become members of the NATO, it will imply certain mirror moves on the Russian side. … If there are NATO detachments in those territories, these territories would become a target -- or a possible target -- for a strike."

On Friday's call, Biden, Andersson and Niinistö "reiterated their shared commitment to continued coordination in support of Ukraine and the Ukrainian people affected by the war," according to the White House statement.

-ABC News' Molly Nagle

Secretary of Defense Lloyd Austin spoke to his Russian counterpart, Sergei Shoigu, for the first time since the invasion of Ukraine began, according to a statement from Pentagon press secretary John Kirby.

Austin urged for an immediate ceasefire and "emphasized the importance of maintaining lines of communication," the statement said.

-ABC News' Matt Seyler

Russian troops suffered "significant" loss while attempting to cross a river in the disputed Donbas region of war-torn eastern Ukraine, the U.K. Ministry of Defense said Friday in an intelligence update.

"Ukrainian forces successfully prevented an attempted Russian river crossing in the Donbas," the ministry said. "Images indicate that during the crossing of the Siverskyi Donets river west of Severodonetsk, Russia lost significant armoured manoeuvre elements of at least one Battalion Tactical Group as well as the deployed pontoon bridging equipment."

"Conducting river crossings in a contested environment is a highly risky manoeuvre and speaks to the pressure the Russian commanders are under to make progress in their operations in eastern Ukraine," the ministry added. "Russian forces have failed to make any significant advances despite concentrating forces in this area after withdrawing and redeploying units from the Kyiv and Chernihiv Oblasts."

On Wednesday, the Ukrainian Ministry of Defense released images purportedly showing a wrecked pontoon crossing over the Siverskyi Donets river, with a number of damaged or destroyed armored vehicles on both banks.

"Artillerymen of the 17th tank brigade of the #UAarmy have opened the holiday season for [Russian forces]," the ministry said in a post on Twitter, alongside the photos. "Some bathed in the Siverskyi Donets River, and some were burned by the May sun."

The Ukrainian Armed Forces' Strategic Communications Directorate also tweeted images of the scene, purportedly showing the smoking wreckage after artillery units and land forces "destroyed all attempts by the Russian occupiers to cross the Seversky Donets River."

Jalina Porter, the State Department's deputy spokesperson, is responding to the Russian attack at a Ukraine train station that killed at least 50, saying, "We can no longer be surprised by the Kremlin's repugnant disregard for human life."

Five children were among those killed when Russian rockets struck the station in Kramatorsk in Donetsk Oblast on Friday morning, according to Ukraine's state-owned railway company. At least 100 people were injured, according to Donetsk Oblast Gov. Pavlo Kyrylenko.

Russia has denied involvement in the attack, which occurred as "thousands" of civilians fleeing the Russian invasion were at the train station waiting to be taken to "safer regions of Ukraine," according to Kyrylenko.

"Civilians are killed when they stay in their homes, and they're killed when they try to leave," Porter said. "Actions like these demonstrate why Russia did not belong on the U.N. Human Rights Council, and they also reinforce the U.S. assessment that members of Russian forces are committing war crimes in Ukraine."

Porter declined to say if the department considers the train station attack a war crime, saying, "Assessing individual criminal liability in specific cases is the responsibility of courts, as well as other investigatory bodies. But as the secretary, Secretary [of State Antony] Blinken, has said, 'Those responsible for war crimes and other atrocities committed in Ukraine will be held to account.'"

-ABC News' Conor Finnegan