Federal wildlife officials are investigating a suspicious injury to the leg of one of three grizzly cubs orphaned when their mother was shot and left to die along the Russian River in July.

Twenty-six-year-old Anchorage resident Michael Oswalt has been charged in state District Court with six misdemeanors in connection with the shooting of that sow, and Kenai National Wildlife Refuge supervisory ranger Bill Kent on Wednesday hinted that there could be more charges to come.

"We are continuing our investigation into the shooting of the sow,'' he said.

Kent refused to be more specific, but Alaska Department of Fish and Game biologists who darted two of the three cubs with a tranquilizer gun last week summoned a federal law enforcement officer to the Russian after noting the nature of an injury to one bear that had been limping.

The young male had been thought to have a fishing hook caught in a foot, but Jeff Selinger, Kenai area wildlife biologist for Fish and Game, said no hook was found. Instead, he said, biologists discovered the bear had "puncture holes'' in a leg.

Selinger said he was not at liberty to further describe the wound but admitted that the holes did not appear to have been caused by the teeth of another bear. And, he said, they were of a nature that made him decide it best to call U.S. Fish and Wildlife refuge officer Clayton McDermott to the scene.

Kent refused to say whether investigators think the cub was hit by a bullet. There have been no reports of anyone shooting at the cubs since their mother died, he said.

Charging documents filed against Oswalt say that on July 31 he fired four rounds from a 7.62 x 39 mm assault rifle in the direction of a sow and three cubs. The sow was found dead a couple of days later. Two bullets eventually were recovered from her body, one of which was ballistically matched to one of a pair of SKS semiautomatic rifles owned by Oswalt, according to charging documents. The SKS is a Chinese-made copy of the well-known Russian AK-47 assault rifle.

A third bullet is thought to have hit the sow somewhere in the body and damaged internal organs, according to charging documents. The whereabouts of the fourth bullet is unclear, although the charging documents suggest it too might have hit the sow in the body. Even if that is the case, there remains a possibility a bullet could have passed through the sow and hit another bear.

Oswalt, according to charging documents, loaded his rifle with "122-grain, full-metal-jacket, .30 caliber bullets." Unlike soft-nosed hunting bullets, which are designed to expand with maximum killing force when they hit flesh, full-metal-jacket bullets are designed to shoot through. Hunting guides and veteran hunters say it would be quite possible to shoot through one animal and hit another behind it, depending on where the second animal was standing.

The position of the Russian River bears at the time of the shooting is unknown.

Oswalt, according to charging documents, has told investigators he saw the family of bears fishing in a pool along the Russian, "dropped his bags, unfolded the stock on his gun, got down on one knee and fired a shot at the bears in the middle of the group. Oswalt said he watched the bears for about a minute after he shot, and the bears were standing in the pool.

"After the first shot, the bears started 'acting weird' and looked like they were going to come toward Oswalt and (fishing buddy Aaron) Carter, so Oswalt said he shot three more rounds towards them. After shooting, Oswalt said he turned around and ran back up the trail, and Carter followed shortly after him.''

Oswalt has not said where he was aiming the rifle when he started shooting. But, according to the charging documents, Carter has told investigators that "after they ran away, Oswalt said he though he hit one of the bears."

Selinger, the state wildlife biologist, said the injury to the cub -- whether a bullet wound or not -- does not appear to be life-threatening. The bear is limping, he said, but is able to put some weight on the bum leg.

The bear, thought to be a 2-year-old boar, is "a little skinny for this time of the year," Selinger said, but otherwise fine. His sister, the biologist added, is in great shape. Judging from tooth development, Selinger said both appear to be 2-year-old cubs, but they could possibly be very large yearlings.

Biologists fitted both of the animals with ear tags after they were captured, discussed whether to relocate the animals, and in the end decided to leave them at the Russian. The consensus was that it was the place where the animals have the best chance of survival.

The biologists have not been able to capture the third cub.

"That's the country they know," Selinger said. "People are going to have to be aware ... (but) this should be quieting down.''

Salmon returns to the ever-popular Southcentral Alaska stream have been slowing. Bears soon will be moving higher into the Russian drainage, where people are relatively rare, to pursue salmon as they move toward their spawning grounds, or relocating toward favorite berry-picking areas as fruits ripen.

Selinger said he is optimistic about the cubs surviving. The untagged cub has become quite secretive since the sow was shot, he said, and the others seem to have developed more awareness as to the dangers of people.

"They can probably make it on their own,'' he said.

Daily News outdoor editor Craig Medred can be reached at cmedred@adn.com