Adam Lanza, the troubled nerd who turned a Connecticut school into a slaughterhouse, learned how to shoot under the watchful eye of his demanding mom Nancy.

“She said she would often go target shooting with her kids,” landscaper Dan Holmes said.

Nancy Lanza wound up being the first of her son’s 27 victims when he used one of her guns to shoot her dead.

Holmes, who often mowed the grass at the Lanza’s sprawling Newtown home, told Reuters the doomed mom was proud of her arsenal and once showed him a “high end rifle” she had just purchased.