The Frozen Ground

The film opens in an Anchorage motel room in 1983, where 17-year-old Cindy Paulson is handcuffed and screaming for help. She is rescued by an Anchorage Police Department patrol officer. He takes Paulson to the hospital, and her clothes are kept for a rape kit. At an APD station, she explains to detectives that she was abducted and repeatedly raped. Because she is a prostitute and lying about her age, the detectives don't believe her story, refusing to even look into the man she named as her abductor, Robert Hansen. They claim Hansen is an upstanding member of society, a family man who owns his own restaurant, and has alibis from three people.The APD patrol officer who rescued Paulson is outraged that the detectives refuse to pursue Hansen. He surreptitiously photocopies information about the case and sends it to the Alaska State Police. Meanwhile, state trooper Jack Halcombe has been called to investigate a female body that was found in the bush, half eaten by bears. The police connect the case to other missing girls, who have disappeared after going to what they thought were legitimate photo shoots. With secret information from the APD officer, Halcombe connects the other cases to Paulson's and starts to put together a portrait of Hansen. Paulson details how Hansen kept her captive, and that she escaped from his car when he tried to transfer her to his bush plane.Meanwhile in Anchorage, Debbie Peters gets picked up by a man in an RV for a photo shoot. Later, Hansen eats a quiet dinner at home. His wife and children are away, and Hansen relaxes in his trophy room, casually ignoring Debbie who is chained to a post. She has urinated on the floor, and as she cleans up the mess with a towel, Hansen's neighbor enters the house to deliver a plate of food. Hansen warns Debbie not to scream and leaves the trophy room to greet his neighbor. Hansen then takes Debbie to the airport, where he orders her into his plane. After landing in a remote spot in the bush, Hansen frees Debbie, letting her run in a panic through the woods before he shoots her with a .223 caliber rifle. He steals her necklace before finishing her off with a handgun.Halcombe has a very difficult time assembling a case against Hansen. Because the evidence is circumstantial and Paulson is afraid to testify, the District attorney refuses to issue a search warrant. Paulson keeps falling back into the world of stripping and prostitution, despite Halcombe's efforts to keep her safe. At a strip club, while she is trying to sell lap dances, she notices Hansen trolling for a new victim. Their eyes meet, a chase ensues, and Paulson barely escapes. The encounter makes Hansen nervous, and he hires Carl Galenski to find and kill Paulson. Carl approaches Paulson's erstwhile pimp Clate Johnson (50 Cent) and offers to forgive his sizable debt if Clate turns Paulson over to him.Halcombe stakes out Hansen's house, causing Hansen to panic. Hansen gathers the evidence of his crimes, including the keepsakes from his victims, and flees with his son to the airport. He flies his plane to the bush and hides his keepsakes. Feeling that the chance to catch Hansen is slipping away, and with the victim count now at 17 girls, Halcombe forces the DA to issue a warrant. The search of Hansen's house yields no evidence, not even in his trophy room. Hansen agrees to be interrogated without a lawyer, but he is not yielding any new evidence. Halcombe arrests Hansen, but unless the police find new evidence, they will be unable to hold him.Halcombe orders a second search of Hansen's house, which turns up a hidden cache of guns, including the .223 caliber rifle used in many of the murders. Under police watch at a safe location, Paulson slips away and returns to her life of prostitution. Clate picks her up and delivers her to Carl. When Clate attempts to rob Carl, Paulson uses the opportunity to escape, with Carl in pursuit. After making a call to Halcombe, Paulson is almost killed by Carl, but Halcombe rescues her just in time.Halcombe uses a bracelet identical to one worn by one of the victims in order to trick Hansen into thinking the police have found where he hid the evidence in the bush. The bracelet, combined with the sight of Paulson in the interrogation room, enrages Hansen to the point that he incriminates himself. The epilogue states that Hansen confessed to the murder of 17 women and the kidnap and rape of another 30. He was charged with the abduction and rape of Cindy Paulson and the murders of Joananna Messina, Sherry Morrow, Paula Goulding and "Eklutna Annie." He was sentenced to 461 years plus life without parole. Robert Hansen died in 2014 at the age of 75. Only 11 of his victims bodies were recovered. Jack Halcombe remained with the Alaska State Trooper and was promoted. He is now retired. Cindy Paulson now lives in the lower 48 and married with 3 children.The film ends with a dedication and actual pictures of Hansen's victims.

Question: What weapon did Hansen use in many of the murders?
Answer: .223 caliber rifle