Months before authorities said he walked into a Florida high school and killed 17 people, Nikolas Cruz was reportedly filmed shooting what appears to be a BB gun in his backyard.

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According to CNN, the video appears to show Cruz, the 19-year-old police say was behind Wednesday's deadly mass shooting at Marjory Stoneman Douglas High School in Parkland, pointing a BB gun outside his house. The person in the video waves the replica weapon around, aims and shoots toward the fence surrounding the house.

The footage is thought to have been taken by a neighbor in October 2017.

Cruz reportedly has a history of disturbing behaviorAccording to police reports obtained by CNN, Cruz was accused of being violent toward his late adoptive mother, who once told Broward County sheriff's deputies that Cruz had expressed an interest in obtaining a gun and cut his arms "for attention." Classmates also said Cruz was abusive toward his ex-girlfriend, the New York Post reported.

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The Federal Bureau of Investigation was previously alerted to Cruz and threats he allegedly made online, including one about wanting to carry out a school shooting.