To be clear, it wasn’t just an idle threat. His mother overheard him trying to acquire a rifle illegally, and turned him in.
It was Cruz’s mother who called the police and reported threats that her son had made, Officer Nick Soliz of the San Antonio Police Department tells NPR.
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The mother “overheard a phone conversation the suspect made this morning in which the suspect attempted to acquire an AR-15 through an illegal private sale” according to the arrest warrant. When confronted by police, Cruz denied making any threats, the warrant states.