Federal prosecutors have charged Douglas Haig, a man identified earlier this week as "a person of interest" in the Las Vegas mass shooting, with selling bullets he had modified to make them more potent - referred to as armor-piercing, NPR reports.
The 55-year-old aerospace engineer did not have a license to manufacture and sell the armor-piercing bullets he sold to Stephen Paddock in the weeks before the massacre that left 58 people dead. Paddock died at the scene from an apparently self-inflicted gunshot wound.
Court documents filed Friday indicated Haig also sold Paddock 720 rounds of tracer bullets.
Haig came to investigators' attention early on, when they found a shipping box with his name on it among Paddock's possessions, reports NPR's Martin Kaste.
Authorities also found Haig's fingerprints on armor-piercing bullets recovered from Paddock's Mandalay Bay hotel room. The ammunition found at the scene was unfired, and it's unclear if any of it was used in the attack.