Following the Cambodian premiere of Angelina Jolie’s new film First They Killed My Father in Siem Reap, Cambodia Saturday, co-screenwriter, rights activist and author of the book that inspired the movie, Loung Ung, spoke to PEOPLE about what it was like working on set, the challenges of portraying the Cambodian genocide on film and eating tarantulas to lighten the mood among the cast and crew. Ung, who has been friends with Jolie since First They Killed My Father was published in 2001, said that there was a real “family feel” on set, with Jolie’s son Maddox, 15, helping with production and her second eldest Pax, 11, shooting stills. “I have watched the young people grow into really kind, empathetic, curious human beings,” Ung tells PEOPLE.