Just before 7 A.M. on March 2nd, at his home on a quiet street in a suburban part of Austin, Texas, Anthony Stephan House opened a cardboard box that had been left outside his front door overnight and it exploded, killing him. The method of the murder was exotic, but at first House’s death attracted little attention, perhaps because the details of his life were relatively mundane. “He was quiet and technically minded—an intense person,” Nelson Linder, the longtime head of the local chapter of the N.A.A.C.P., who had once hired House to build a Web site for the group and who was close with House’s stepfather, explained to me in Austin last week. “You can see it in the photos—he is usually not smiling.” House lived on a street with many similar, one-story brick-fronted structures; he had served at one point as the president of his neighborhood’s homeowners’ association. He worked in the construction industry, as a project manager. He was thirty-nine years old, married, and had an eight-year-old daughter, who was at home when the bomb detonated.

It wasn’t obvious, at first, whether the bomb had been intended for House, or for someone else, or for no one in particular—whether its aim was specific violence or a more generalized mayhem. When someone is killed with a gun, certain established forensic clues (the position of the victim’s hand and body, the pattern of gunpowder spray) help the police rule out suicide. With a bomb, things are less certain. “We can’t rule out that Mr. House didn’t construct this himself and accidentally detonate it, in which case it would be an accidental death,” Joseph Chacon, the assistant chief of police in Austin, said at a press conference three days after House was killed, to explain why the department was not yet treating the incident as a murder. Within a few days, the interim police chief, Brian Manley, would advance another theory: a home a few doors down from House’s—one that looked very similar, with a very similar-looking car parked outside—had been raided by cops as part of a drug investigation a few days before the explosion. Perhaps the bomb, Manley suggested, was a “retaliatory act,” meant for someone else but mistakenly placed on House’s doorstep.

A notable fact about House was the identity of his stepfather, the Reverend Freddie Dixon, who has been a prominent figure in Austin’s black community since the seventies. Dixon used to run one of the city’s most prominent churches—Wesley United Methodist Church—and helped found the city’s chapter of the Urban League. He has also been influential in the local N.A.A.C.P. “A very political man who wanted to improve the position of African-Americans, and fought for it,” Dixon’s successor at Wesley United Methodist Church, the Reverend Sylvester Chase, Jr., told me. To some within the established black community in Austin, the Reverend’s stature gave his stepson’s death another layer of uncertainty. Why had the quiet son of the crusading minister been killed in such an unusual manner, and under such mysterious circumstances?

On March 12th, another package exploded on the east side of Austin, this one at a home ten miles farther south, off East Martin Luther King Junior Boulevard. The bomb killed a seventeen-year-old student, Draylen Mason, and injured his mother, Shamika Wilson. The two had been preparing for a morning workout. Mason, a high-school senior, was an exceptional teen-ager, the lone black member among the seventy-six musicians in the Austin Youth Orchestra. One of the paramedics who responded to the scene, by coincidence, was the son of a member of the orchestra’s board, and so the Austin classical-music community knew that Mason was dead before his name was on the news.

When the news reports did arrive, Mason came across as a vivid character—boisterous and warm—whose ambition and ability were obvious to the adults around him. He had a habit of tracking down famous bass players online, friending them on Facebook, trying to start e-mail relationships. Dana Wygmans, an Austin bass player who had tutored Mason weekly since he was twelve, told me, “I think Draylen loved being someone that the other musicians could rely on.” For some people who knew him, Mason captured a certain liberal aspiration for what the city could be. “It made me proud of Austin that it could produce someone like Draylen,” William Dick, the conductor of the Austin Youth Orchestra, said.

Mason and House did not know each other, yet they had a connection. Mason’s grandfather, Norman Mason, was a Howard-educated dentist, a partner at a prominent dental practice in historically black eastern Austin. His wife, LaVonne, had co-founded the Austin-area Urban League, and the two of them were close friends with Reverend Dixon, House’s stepfather. More than nine hundred thousand people live in Austin, and it seemed statistically impossible that the stepson of one prominent black figure could be killed by a bomb dropped off at his door and then, ten days later—ten miles away—the grandson of a second prominent black figure would himself be killed by the same method. “It’s not just coincidental. Somebody’s done their homework on both of us, and they knew what they were doing,” Dixon told a reporter.

The pattern of the bombings, and their anonymity, made them seem designed to terrorize, and speculation had begun to spread—national papers suggested that someone was targeting prominent African-American citizens in Austin, and suspicions on social media tended to point to white supremacists. Dick, the youth-orchestra conductor, told me that after Mason’s killing he had been able to envision a very specific perpetrator: “in his forties, white, a veteran.” For people who believed that Austin was a different kind of place, it made a certain sense that its difference would also make it a target. “My diagnosis: Number one, I think it’s a hate crime,” Dixon said. “Number two, somebody’s got some kind of vendetta here.” For the families, it did not seem plausible that the murders were random. There was instead a pattern—something to be explained.

Just a few hours after Draylen Mason was killed, a third bomb detonated, at a home about five miles south of Mason’s, on Galindo Street in southeast Austin, where it injured a seventy-five-year-old woman named Esperanza Herrera, who was visiting her mother, Maria Moreno. This bomb offered some relief, in that it did not kill, but it was also confounding, because Herrera had no obvious connection to the Mason or Dixon families. Quickly, though, police sources told local reporters that they had a theory. One of Moreno’s neighbors was a hairdresser named Erica Mason. Perhaps, the police thought, the bomber had been under the mistaken impression that she was related to Draylen. Even by the time I arrived in Austin, more than a week later, people were still talking about Erica Mason as if she were African-American. But she turned out to be white, which made the conviction that Galindo Street had been targeted because the bomber thought it was home to a distant Mason cousin a little bit more of a stretch.

At this point the bombings became national news, and some five hundred law-enforcement officers, many of them federal agents, were working on the case. Chief Manley told reporters that the police were “very conscious” of the racial dimensions of the attacks—that all of the victims had been black and Hispanic. The exact nature of the racial connection was not specified, though. This troubled Linder somewhat. He understood the delicate nature of the situation, the potential for the nation’s social conflict to concentrate in his city. “I was getting calls from my national”—the Baltimore headquarters of the N.A.A.C.P.— “saying, ‘What’s happening? Should we be out in the streets?’ ” Linder said. “I told them, ‘Trust me on this. It’s just my gut, but I don’t think this is a hate crime.’ ”