Out of nowhere on Tuesday night, around 8 PM, Alex Arevalos, a student and graphic designer in Alhambra, California, ten miles east of downtown Los Angeles, heard a single, loud thud. He immediately asked his sister if she'd slapped his bedroom wall. "She said she didn't, so I automatically blamed the train," Arevalos, who lives near train tracks, told VICE. Then on Thursday around midnight, two similar sounds woke up Arevalos's father, and when father and son spoke about it in the morning, the younger Arevalos became convinced it was something abnormal. "This time as soon as I heard it, and heard the walls shake a bit, I listened for the train, but didn't hear anything," adding, "I can tell the difference now [between] the train and the booms." Arevalos is far from alone. According to the local news site Alhambra Source, residents first reported hearing the booms on February 16 when a woman named Noelle Dominguez alerted her neighbors to them in a private section of the community