As noted previously, the Orlando nightclub shooter had worked for security contractor G4S since 2007, and the contractor, previously known as Wackenhut, provided security services at the Y-12 nuclear weapons plant for more than a decade — from 2000 to 2012. But a federal spokesman at Y-12 confirmed that Omar Mateen had never worked at Y-12 or had any association with the Oak Ridge plant.

“There is no indication or any record whatsoever that this individual has been at Y-12 or has possessed an access authorization,” Steven Wyatt of the National Nuclear Security Administration said in an email response to questions.

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