It was mid-afternoon on September 28, 2021, when Antelmo Ramirez began acting strange. A 57-year-old originally from the Mexican state of Nuevo León, Ramirez was working at the sprawling construction site of the Tesla Gigafactory just southeast of Austin, building wooden forms for a concrete pour. He was average height, built sturdy, with short salt-and-pepper hair and stubble to match. According to his oldest daughter, he was a reserved man, th…