As authorities continue searching for the 74-year-old Rancho Cucamonga man missing since May, family members now believe that he was likely kidnapped by someone.

“He’s kind of a guide to my life, for a very long time,” said Wen Hou. “I just want my dad back.”

His father, Nai Ping Hou was reported missing by family on May 4, but they say things have been different since March, when he became unusually detached in their family group chat.

“Over time, when I ask if he wants to come meet up with us, you know, I have young children so it’s harder for me to travel to him, he would say either he’s tired, or ‘I’ll call you later,’ or ‘I can’t meet,'” Hou said. “But, he’s a semi-retired grandpa right now, so that’s really strange.”