The FBI has joined the search for a missing Southern California grandfather as authorities escalate what is now being treated as a kidnapping investigation tied to a troubling web of fraud, impersonation and possible targeting linked to cryptocurrency wealth.

Nai Ping Hou, 74, vanished in March 2025 from his Rancho Cucamonga home and was reported missing weeks later on May 4.

Federal officials say possible foul play is suspected, noting Hou’s bank accounts were depleted before law enforcement was even notified of his disappearance.

Investigators with the San Bernardino County Sheriff’s Department initially described the case as a suspicious disappearance but now say evidence points to a possible abduction.

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Hou’s son Wen Hou said the last time he saw his father was during a fishing trip in March, just days before he disappeared.

“He was in a very good mood,” Wen Hou told KTLA. “He caught a lot of fish. His friends were there, too. He was very happy.”

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But weeks later, subtle changes raised alarm.

“[Always saying] he’s tired or he’ll call me later, just reasons that were strange,” he said. “He had very short responses and didn’t share photos anymore.”

Wen Hou said the moment it truly set in came when his father stopped answering calls altogether and sent an unusually cold message on his birthday.

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“It’s surreal to think someone could be impersonating my dad through text,” he previously told KABC.

The family said that’s when they realized something was seriously wrong and grew deeply concerned for his safety.

When friends went to check on Hou’s home in early May, they found it had been completely cleared out.

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“Something really bizarre is going on,” Wen Hou said. “The place was completely cleared out. No people, no vehicles, not even garbage left behind.”

Investigators later confirmed “extensive fraudulent activity” in Hou’s bank accounts around the time of his disappearance. More than $1 million was drained through unauthorized transactions, including purchases of gold and cryptocurrency.

“His money was also gone,” Wen Hou said. “Funds were being transferred out to purchase gold online. He’s not tech-savvy at all, so I don’t know how he could’ve done any of that himself.”

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Authorities say Hou’s vehicles were also sold and there was an apparent attempt to rent out his home.

Hou’s wife was out of the country visiting family in China at the time he vanished and received unusual messages from his phone, including one suggesting she delay returning home.

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While investigators have not confirmed a motive, the family has told KABC they fear Hou may have been targeted because of their financial success in cryptocurrency. Wen Hou is a hedge fund executive who has invested heavily in the space.

“I miss him dearly,” Wen Hou said. “He’s always been a guiding presence in my life.”

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“We’re really worried, and we really want my dad back,” he added.

Hou is described as 5 feet 7 inches tall and about 170 pounds, with dark hair and a birthmark on his upper left shoulder. He also has a surgery scar on his lower back. He has not been seen or heard from since March 2025.

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Investigators are also seeking information about a silver Toyota Yaris believed to be connected to the case.

The Hou family has launched a dedicated website to raise awareness, share photos and collect tips. The site includes a video message in which Wen Hou makes an emotional plea for his father’s safe return.

A reward of up to $250,000 is being offered for information leading to Hou’s safe return or the arrest of those responsible.

Authorities urge anyone with information to contact the San Bernardino County Sheriff’s Department or the FBI.