UPDATE: Police say the third man accused in the killing, Kennith Upton, 23, was taken into custody at about 2 p.m. today in Mountain View.

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Three men have been charged with murder in the killing of a 23-year-old man who may have been beaten to death over the theft of a backpack. Police said they believe a body found Tuesday night along a riverbank outside Anchorage is that of the victim.

Two of the suspects are in jail. Another is on the loose, according to police.

The victim, Harvey "Charley" Albright, was reported missing Aug. 25 from Eagle River. Friends and family members told police he was often in touch with them, but communications suddenly stopped.

In custody are Philip Floor, 24, of Chugiak, and Carl Leedom, 23, of Eagle River. Detectives are looking for a third man, 23-year-old Kennith Upton.

Police say Albright had stolen a backpack -- with cash and other items --from Leedom. Witnesses told police Leedom threatened to kill Albright over the theft and that the men severely beat and pistol-whipped him to "teach him a lesson."

The night of Aug. 24, Leedom and Albright were staying at Upton's Eagle River home, witnesses told police. There, Leedom confronted Albright about the stolen backpack.

Early the next day, Leedom invited Floor to the home, where they began beating Albright as he slept on the couch, police say.

The sound of the assault woke Upton, who soon joined in, according to police.

Albright stopped breathing after Leedom began hitting him with a handgun, police say.

Leedom told the others to put the body in a pickup, which he and Floor drove to a riverbank outside of Anchorage, according to police. As Upton stayed behind to try to clean the crime scene, Leedom and Floor dumped the body, police say.

Detectives aren't naming the river where the body -- tentatively identified as Albright's -- was found.