A Coast Guard rescue swimmer is being held at a Navy-run facility in Pearl Harbor while the military service investigates his three-month disappearance as it prepared to discharge him for illegally using marijuana.

The Coast Guard on Wednesday launched a weeklong review of Petty Officer 1st Class Russell Matthews’ case, spokesman Chief Warrant Officer Gene Maestas said. 

He hasn’t been arrested. But his commanding officer, Capt. Timothy Gilbride, the commander of Coast Guard Air Station Barbers Point, ordered Matthews confined because of his unauthorized absence and the circumstances surrounding his disappearance make it possible he could take off again, Maestas said. 

Matthews showed up at his home over the weekend, more than three months after his wife reported him missing and government agencies launched an extensive search for him both on land and at sea. 

Honolulu police said Matthews returned home Sunday, but he was incoherent and taken to a hospital for observation. He later called his command.

Tripler Army Medical Center released Matthews on Tuesday night.

When the 36-year-old vanished in October, he was in the process of being discharged from the Coast Guard for illegal use of marijuana, Maestas said.

Maestas said he doesn’t know where Matthews has been or what he’s been doing but that would come out in the investigation.

“We want to know, too,” he said.

Matthews is a rescue swimmer with 15 years of experience in the Coast Guard. He’s been stationed at Air Station Barbers Point on Oahu for five years.

In October, police found the guardsman’s car abandoned at Kaena Point, a remote area of Oahu next to the ocean. At the time, police described him as being emotionally distraught and said his friends and family were concerned for his welfare.

Matthews’ first wife was in a critical accident in 2009, and committed suicide in 2011, according to local news reports. 

Search and rescue crews scoured more than 10,000 square miles looking for Matthews. Honolulu firefighters sent a helicopter and rescue teams to conduct aerial and ground searches of the rugged coastline and sand dunes near Kaena Point. 

“We wanted to make sure he wasn’t hurt in some area inshore,” Honolulu Fire Department spokesman Capt. Terry Seelig said.