Oliver Calibet expressed frustration in the lack of assistance from the U.S. and Greek governments in the search for his brother Albert.
The video in the player above is from an earlier report on the search.
And with no sign of his brother's body after nearly three weeks, he suspects foul play.
"It is with heavy heart that I announce the conclusion of our search for our beloved Albert," Oliver Calibet wrote. "Despite our relentless efforts and determination, Albert remains missing. I deeply fear that foul play has occurred as we found zero evidence of Albert anywhere on the island.
Albert Calibet, 59, of Hermosa Beach, was reported missing on June 11 on after he went for a hike on the Greek island of Amorgos on a hot day and didn't show up to meet a friend afterward for lunch.
Retired LA County deputy disappears while hiking in blistering heat wave in Greece
Albert's girlfriend and his brother flew to Greece to personally search for him after saying the Greek government and the U.S. embassy were not being helpful. Los Angeles County Sheriff's Department volunteers also joined the search.
"Throughout this ordeal, we encountered numerous obstacles and roadblocks from the Greek authorities, which hindered our search and added to our anguish. There was little assistance from the US Embassy. As a result, we have left the island fearing for our own health and safety; endless hiking of the island was taking a huge toll on our bodies."
Among the roadblocks, he said, he was not allowed access to cellphone tower data.
There have been at least five reports of foreign visitors to Greek islands going missing or dying in recent weeks.