Midwest City, Oklahoma: Midwest City Police have released surveillance video from a Walmart of a man who took a 2-year-old girl from a mother's shopping cart, and held a knife to the child's throat. Police Chief Brandon Clabes held a news conference Friday morning to reveal new details about the June 17 officer-involved shooting. Capt. David Huff shot and killed 37-year-old Sammie Lamont Wallace after he threatened the little girl.The video released shows Wallace walking into the Walmart Neighborhood Market at Reno and Midwest Boulevard around 3 p.m. He's pushing a shopping cart and talking on a cell phone. The video shows Wallace circling the store until he sees a woman, identified as Alicia Keating, and her two daughters, ages 12 and 2. Wallace keeps walking but circles back to the frozen food aisle. While Keating's back is turned, Wallace grabs the child from the cart while the stunned 12 year old looks on. Wallace then walks up to the mother, hands her a cell phone and demands she call a police officer in Dallas. Keating begins to scream and pleads for the man to give her child back. The man pulls out a knife and threatens the little girl. That's when store employees approach the man and witnesses begin calling 911.The Midwest City Police Department is just across the street from the store, and officers arrive within a minute. They quickly evacuate the store, including the little girl's mother. Chief Clabes says officers tried to negotiate with Wallace for more than half an hour. They eventually contacted the police officer in Texas he wanted to speak with, and the officer said Wallace had been harassing him.Clabes says toward the end of the standoff, they offered Wallace a chair to get a "tactical advantage." Wallace sat, but became increasingly agitated. Clabes says up until that point, the little girl had been calm and quiet; but Wallace began squeezing her so she started to squirm. Clabes says when the girl began squirming, Wallace moved the knife from her abdomen to her neck. Wallace also mentioned a satanic cult, and started a 60-second countdown. Clabes says Capt. Huff believed Wallace was either about to or had already harmed the child with the knife. He approached Wallace as he was seated in the chair, and shot him in the head. Wallace was killed instantly.Clabes said Wallace was in a Texas prison from 2000 to 2011. His family told police he had a long history of mental illness. Wallace reportedly moved to Oklahoma earlier this year after he claimed to have seen a ghost in his apartment. The child who was held hostage is fine. The Oklahoma County district attorney said the shooting was justified, and hailed Capt. Huff as a hero.Original news report by www.news9.com CCTV footage - 11 minutes narrated by police and censored - no gore:Another news report with more background on kidnapper:Sammie Lamont Wallace: