"Ukrainian refugees need humanitarian corridors," Matthew tweeted. "Halyna's family is trapped in Kyiv because of the danger of travel. Her mother continues to work in the hospital where she has been a nurse for over a decade because her country needs her, but also because they cannot leave safely."
In separate tweets, Matthew wrote about the need for "a no fly zone" in Ukraine and encouraged people to "support refugees and the territorial defense force with aid and any intervention possible to protect the Ukrainian citizens and their independence."
Following Matthew's tweets, a rep for the widower told ET, "Halyna's sister and 3-year-old niece have just made it to the Romanian border, attempting to get evacuated."
Halyna, a cinematographer, died in October when Alec Baldwin discharged a prop gun on the set of the film Rust. Baldwin spoke out on Good Morning America in December, saying he felt grief but not guilt for Halyna's death. He also claimed that he did not pull the trigger on the prop gun that killed Halyna.
In February, Halyna's estate filed a wrongful death lawsuit against the Rust production and Baldwin, who acted in and produced the film, over the fatal shooting.
In a news conference, lawyers for Halyna's estate said that Baldwin, as well other named defendants, are "responsible for the safety on the set and whose reckless behavior in cost cutting led to the senseless and tragic death of Halyna Hutchins."
"Any claim that Alec was reckless is entirely false. He, Halyna and the rest of the crew relied on the statement by the two professionals responsible for checking the gun that it was a 'cold gun' – meaning there is no possibility of a discharge, blank or otherwise," lawyers for Baldwin and the Rust production said in part in a statement to ET. "This protocol has worked on thousands of films, with millions of discharges, as there has never before been an incident on a set where an actual bullet harmed anyone."
Days later, in an interview with the Today show, Matthew expressed anger toward Baldwin and the statements he made during his GMA interview, saying it "almost sounds like he was the victim."
"I was just so angry to see him talk about her death so publicly, in such a detailed way and then to not accept any responsibility after having just described killing her," Matthew said. "The idea that the person holding the gun causing it to discharge is not responsible, is absurd to me. But gun safety was not the only problem on that set. There were a number of industry standards that were not practiced and there’s multiple responsible parties."