When Pentagon press secretary John Kirby Kirby was asked at Friday's briefing whether he believes Russian President Vladimir Putin is a rational actor, he first responded by saying he couldn't speak to his psyche, adding, "It's hard to look at what he's doing in Ukraine, what his forces are doing in Ukraine, and think that any ethical, moral individual could justify that."

Kirby then appeared to get choked up and paused for several seconds. He said, "Sorry, it's difficult to look at some of the images and imagine that any well-thinking, serious, mature leader would do that. So I can't talk to his psychology, but I think we can all speak to his depravity."

Kirby later apologized, saying, "I didn't mean to get emotional. I apologize for that. I don't want to make this about me. But I've been around the military a long, long time and I've known friends who didn't make it back. It's just hard."

He went on, "It's difficult to look at that and it's hard to square his -- let's just call it what it is, his BS: This is about Nazism in Ukraine, and it's about protecting Russians in Ukraine, and it's about defending Russian national interests when none of them, none of them were threatened by Ukraine. It's hard to square that rhetoric by what he's actually doing inside Ukraine to innocent people. Shot in the back of the head, hands tied behind their backs. Women, pregnant women being killed. Hospitals being bombed. I mean, it's just unconscionable."

Kirby announced at Friday's briefing that the U.S. has started "training with Ukrainian armed forces on key systems at U.S. military installations in Germany."

"These efforts build on the initial artillery training that Ukraine's forces have already received elsewhere, and also includes training on radar systems and armored vehicles that have been recently announced as part of security assistance packages," Kirby said.

-ABC News' Matt Seyler

Pentagon press secretary John Kirby told CNN Friday that Russian President Vladimir Putin "absolutely shouldn't be" at the G-20 summit, set for November in Bali.

"He has isolated Russia by his own actions and he should continue to be isolated by the international community," Kirby said.

"I can't speak for President Biden or what the schedule might offer for the president, for United States attendance. But it's inappropriate, I think, for the entire international community to keep treating Russia as if things were normal, because it's not," Kirby said.

-ABC News' Matt Seyler

At least one person -- a journalist -- was killed in a rocket attack on a residential building in Kyiv on Thursday evening, ABC News has learned.

Kyiv Mayor Vitali Kilitschko said Friday that rescuers had found the body of a victim amid the rubble.

Radio Liberty, a service of the U.S.-funded Radio Free Europe/Radio Liberty, reported that one of its employees, Vira Gyrych, was killed when a Russian missile hit her apartment in the Ukrainian capital on Thursday. Her body was found beneath the wreckage Friday morning, according to the report.

Gyrych had worked as a journalist and producer for Radio Liberty's Kyiv bureau since 2018. Prior to that, she worked for leading Ukrainian television channels, according to Radio Liberty.

"The editorial staff of Radio Liberty expresses its condolences to the family of Vira Gyrych and will remember her as a bright and kind person, a true professional," Radio Liberty said in its report.

Israeli Ambassador to Ukraine Michael Brodsky also confirmed Gyrych's death in a Twitter post, saying she was a former employee of the Israeli embassy in Kyiv.

Thursday's rocket attack came as United Nations Secretary-General Antonio Guterres visited Kyiv. Five Russian missiles flew into the city, according to Ukrainian President Volodymyr Zelenskyy. At least 10 people were injured, including four who were hospitalized, according to the Kyiv City Council.

United Nations Secretary-General Antonio Guterres admitted Thursday that "the U.N. Security Council has not been able to do everything in its power" to resolve the war in Ukraine, as he pledged to "fight with the use of force."

"We will not give up," Guterres said during a joint press conference with Ukrainian President Volodymyr Zelenskyy in Kyiv.

According to Guterres, U.N. staff are already providing on-site assistance in 30 locations across Ukraine. The U.N. chief called Russia's invasion of Ukraine "a violation of the U.N. Charter." One of the organization's values, he said, "is the need that territorial integrity of the countries must be respected."

"This is fundamental," Guterres added.

Guterres visited Kyiv as the Ukrainian capital was hit by two missile strikes on Thursday evening. Five missiles flew into the city, according to Zelenskyy. At least 10 people were injured, including four who were hospitalized, according to the Kyiv City Council.

"This says a lot about Russia's true attitude to global institutions. About the efforts of the Russian leadership to humiliate the U.N. and everything that the organization represents," Zelenskyy said in his nightly broadcast.

Earlier on Thursday, Russian Foreign Ministry spokesperson Maria Zakharova accused Western countries of openly calling on Ukraine to attack Russian territory with the weapons they supply to Kyiv.

"We have already commented the other day on statements by British Deputy Defense Minister [James] Heappey about okaying Ukraine's strikes on Russian military targets," Zakharova told reporters in Moscow, according to Russian state media. "In other words, the West is openly calling on Kiev to attack Russia, even with weapons received from NATO countries."

According to Zakharova, Kyiv has taken this as a guide to action, evidenced by the Ukrainian military's shelling of Russian border territories over the past few weeks that resulted in casualties and destruction. Zakharova said the Ukrainian strikes were "further evidence that Zelenskyy's regime is not independent in its decisions and is completely dependent on external handlers."

Zakharova also stressed that such "criminal activity" of the Ukrainian military against Russian territory cannot go unanswered.

"I would like Kyiv and Western capitals to take seriously the statements of our country's defense ministry that further Ukrainian provocations to strike Russian targets will definitely lead to a harsh response from Russia," she said.

At a press conference in Vienna on Thursday, International Atomic Energy Agency Director-General Rafael Grossi warned that Russian missiles over Ukrainian power plants could cause a nuclear accident. Grossi, who recently visited Ukraine and its Chernobyl nuclear power plant, said the Ukrainian government officially informed his agency, the nuclear watchdog of the U.N., of a video surveillance camera recording the flight of a missile directly over the South Ukraine nuclear power plant near the city of Yuzhnoukrainsk on April 16.

"The IAEA is studying the evidence and if it is confirmed, the incident will have extremely serious consequences," Grossi said. "If such a missile changed its trajectory, it could seriously affect the physical integrity of the nuclear power plant, which could lead to a nuclear accident."

-ABC News' Edward Szekeres, Yuriy Zaliznyak, Uliana Lototska and Nataliia Kushnir

Mariupol has not yet fallen, despite Russia's demands that Ukrainian troops defending the besieged Ukrainian port city surrender, according to Ukrainian Prime Minister Denys Shmyhal.

"There [are] still our military forces, our soldiers, so they will fight until the end," Shmyhal told ABC News' George Stephanopoulos in an exclusive interview Sunday on "This Week."

Mariupol is a strategic city for Moscow because it would allow Russian forces in the south to connect with troops in eastern Ukraine's contested Donbas region. It would also give Moscow a key port.

Although Mariupol remains under the Ukrainian government's control, Shmyhal said the city's residents are suffering.

"They have no water, no food, no heat, no electricity," he said. "They ask all of our partners to support and help stop this humanitarian catastrophe."

-ABC News' Monica Dunn