The White House mourned the accidental killing of three Israeli hostages held by Hamas in Gaza by Israel Defense Forces soldiers on Friday, calling it “a terrible tragedy.”

“It’s just terrible, terrible news,” said White House national security spokesperson John Kirby in an interview with MSNBC. He was not aware of any “connection between today’s tragic events and impacts on the specific safety and security of any other hostages being held.”

“Obviously, we want them all released,” Kirby said of the remaining hostages held by Hamas. “The best safety for them is to get them out now,” he continued. “And Hamas could do that, if they would just do the right thing and release them all, which, obviously, they haven’t proven willing to do.”

The Israeli military released the results of a preliminary investigation on Saturday that determined that the killings were a violation of the IDF’s rules of engagement. The inquiry found that three men, shirtless and carrying a white cloth, approached IDF forces in an area in northern Gaza that has seen heavy fighting. An Israeli soldier shot two of the men dead immediately, while a third escaped to a nearby building, where he called for help in Hebrew and was killed when he came out of the building.

“The IDF emphasizes that this is an active combat zone in which ongoing fighting over the last few days has occurred. Immediate lessons from the event have been learned, which have been passed on to all IDF troops in the field,” the Israeli military said in a statement.

It was not clear as of Saturday whether the hostages had escaped or been abandoned.

In a statement, Israeli Prime Minister Benjamin Netanyahu called the incident “an unbearable tragedy,” adding, “Together with the entire people of Israel, I bow my head in deep sorrow and mourn the death of three of our hostages.”

Hundreds came out to protest in Tel Aviv Friday night, calling on the Israeli government to work to secure an immediate deal for the rest of the hostages still held in Gaza. The Israeli government has reported that Hamas still holds an estimated 137 hostages.

In his comments on Friday, Kirby warned against making a “broad judgment about the specific circumstances” of the hostage killings. “I think the Israelis will certainly take a look at this, and I’m sure they will do the forensics and to try to figure out how this happened,” he said. “That’s certainly the way we would approach a situation like this.”