When Anum Hussain heard about the Boston Marathon bombing, she immediately panicked, worried that the culprits would be like her. The 22-year-old Muslim was in the offices of Hubspot, the Cambridge marketing-software company she works for full-time. As her coworkers frantically rushed to call loved ones who'd been out watching the marathon that day, she was glued to the TV, fearing what she might learn about potential suspects. “My heart was beating fast, just praying that this person didn't turn out to be Muslim,” she recalled. “I knew that if they were, all hell was going to break loose.”