Russia was massing troops on the border with Ukraine when an increasingly desperate Cesar Quintana went to the U.S. embassy in Kyiv in December to plead for a passport for his toddler son, who had been abducted from their Southern California home a year earlier by his Ukrainian-American mother.

Quintana got a U.S. court order showing he had sole legal custody of 2-year-old Alexander. He was granted the passport, bought plane tickets and a few days later headed to the airport for a flight home.

But they never boarded the plane. Police who he said were summoned by Alexander’s Ukrainian grandmother — the mother of Quintana’s estranged wife — ordered the boy be turned over to her.

Now, three months later, Ukraine is ravaged by war. The city of Mariupol where Alexander has been living with his mother at his grandmother’s home is under siege. Quintana, who is back in the U.S., has lost contact with them and is so distraught he’s considering going into the war zone to find his son.

“I am willing to do everything and anything,” Quintana told The Associated Press. “I just want my son to be back.”