SEATTLE (Reuters) - The river otter believed to be responsible for a rare attack on humans that left a Washington state boy and his grandmother badly hurt has been killed, state wildlife officials said on Tuesday. 
 
 The large male otter was trapped, captured and euthanized just yards from where the late July attack occurred in the Pilchuck River in Snohomish County, about 36 miles northeast of Seattle, the Washington Department of Fish and Wildlife said. 
 
 The otter pounced on an 8-year-old boy as he swam to a rope swing, and then turned on the child's grandmother as she tried to intervene, officials said. Both were hospitalized with dozens of bite and scratch marks to the face, arms and chest. 
 
 The attack appeared unprovoked, according to Captain Alan Myers of the Department of Fish and Wildlife. 
 
 "Aggression is not usual for this species," he said. 
 
 In the days after the attack, trappers found several females with pups in the area, and said the responsible animal might have been a mother protecting her brood. However, those females showed no signs of aggression and moved out when dogs came through, Myers said. 
 
 The large male otter found Sunday acted aggressively and did not appear scared of dogs or humans, Myers said. 
 
 "It appears he was very habituated to humans," he said. 
 
 River otters are semiaquatic animals that generally live along river banks and hunt for fish underwater. They are able to hold their breath for about eight minutes. An adult can weigh between 11 and 30 pounds. 
 
 A necropsy will be performed to determine whether disease or previous injury played a role in the otter's unusually aggressive behavior, Myers said. 
 
 (Reporting by Victoria Cavaliere; Editing by Daniel Wallis) ||||| SEATTLE (AP) — Authorities have tracked and killed the otter that attacked a boy and his grandmother as they were swimming in a river near Seattle, state wildlife officials said Monday. 
 
 Federal officials shot the male otter near the place on the Pilchuck River where the attack took place at the end of July, about 30 miles northeast of Seattle, according to Capt. Alan Myers of the Washington Department of Fish and Wildlife's police force. 
 
 Officials said they're nearly certain they got the right otter because of his unusually aggressive behavior. Otters are more likely to avoid people than to attack them. 
 
 The investigation aided by otter experts from the U.S. Department of Agriculture Wildlife Services was originally focused on female otters, because they suspected a mother protecting her pups may have attacked someone she perceived as coming too close. 
 
 When wildlife officials "hazed" female otters in the area, however, the animals left the popular recreational area. 
 
 "This very large male could not be persuaded," Myers said. 
 
 The otter that was shot Sunday afternoon with a .22-caliber pistol with a silencer was at least 4 feet long, officials said. 
 
 A necropsy was being conducted to find out if some disease or injury may have contributed to his aggressive behavior. Although the otter will need to be tested for rabies, the diseases is all but unheard of in otters, Myers said. 
 
 The 8-year-old boy who was attacked needed stiches for bites, and his grandmother was at risk of losing an eye from the attack near Lake Connor Park, which is between Lake Stevens and Machias. 
 
 Both have been released from the hospital, and Myers said the last he heard they were recovering. 
 
 Myers said it's safe to go swimming in the Pilchuck River again, but people should always remember that interactions with wildlife can be dangerous. 
 
 "It's important that people are always aware of their surroundings. When they see wildlife, try to avoid it as much as possible," he said.
– Swimmers are now free to go back in the Seattle-area Pilchuck River without worrying unduly about being attacked by crazed otters, authorities say. Wildlife officials say they tracked, shot, and killed a large, aggressive male otter just yards from where an 8-year-old boy and his grandmother were badly injured in an otter attack last month, reports Reuters. Authorities say they initially suspected a female otter protecting pups attacked the boy as he swam and then attacked his grandmother as she went to his aid, but the male they shot was unusually aggressive and they're pretty sure he was the culprit, the AP reports. The otter, which was at least 4 feet long, appeared to have no fear of humans, authorities say. A necropsy will be carried out to determine whether disease may have played a role in its behavior.