A father putting his hand on the glass of a departing train window as his young son did the same was one of many heartbreaking scenes witnessed in Kyiv on Friday by NBC News' Richard Engel.
Residents in Ukraine's capital city were packed into train stations trying to head west as more than one million Ukrainians flee the country amid the Russian invasion.
Engel, NBC News' chief foreign correspondent, witnessed a father parting with his family as they boarded a train headed out of the city.
"It was one of these heartbreaking moments," Engel said on TODAY Friday. "I was watching a man say goodbye to his family, his wife and his young son. And he was there on the platform. He put his hand up to the glass. His young son on the inside of the train, put his hand up to the glass.
"And I asked the man how he was feeling and he said it was the most difficult moment of his entire life right there as he’s watching his family go away and he’s staying behind to fight."
Engel said scenes like that were repeated throughout the day in the station's chaotic atmosphere.
"There are moments in life, especially wartime, when families have to make very difficult decisions, and people are making those decisions right now," Engel said. "Families are separating.
"We were at the train station and we saw sometimes whole families arriving, saying goodbye on the platform, and then women, children, elderly getting on the train with one or two bags."
Many families are traveling with only a handful of belongings and a vague plan for what comes next.
"There was a lot of pushing, a lot of confusion," Engel said. "People obviously didn't want to miss the train, (and) they're trying to get as many people onboard as possible. And they were all heading west.
"People were heading out of this city. Sometimes they didn't know exactly where they were going or where they would end up, but they were heading toward Lviv and then beyond to Poland or other countries."
The invasion has triggered a humanitarian crisis as more people seek safety during an intensified Russian assault on multiple major cities. More than 1.2 million Ukrainians have fled in a week, with more than 600,000 of them heading to neighboring Poland, according to the United Nations High Commissioner for Refugees.
The United Nations estimates that more than 4 million Ukrainian refugees may need assistance in the coming months.