AUSTIN, Texas — The Baileys convened a family meeting Tuesday morning to answer impossible questions from their four children, and impart advice they never believed they would have to give.

‘‘If you see anything, anything at all, you tell your mother and me,’’ Steve Bailey, an oil and gas executive, told them.

Two evenings earlier, a bomb had exploded a block away, along the route the children walk to the Regents School of Austin, a private school many from the well-to-do neighborhood attend.

A serial bomber, motive unknown, has moved in a clockwise sweep around the city, from northeast to southwest, with sophisticated devices blowing up on doorsteps, in package-sorting centers, and on bike paths. For 18 days, this city of music and technology, education and pioneering cuisine has lived the kind of anxious life that more commonly defines the daily routine in distant, troubled countries.

Two people have been killed so far — a 39-year-old African-American money manager and a 17-year-old African-American student who aspired to be a musician — with several others wounded.

Police responded to a reported explosion and injury at a strip mall south of downtown Tuesday evening, thought at first to be the seventh bomb and sixth explosion in less than four weeks. Authorities later said it was unrelated to the previous blasts.

The morning began Tuesday with bomb squads called to a vast FedEx facility near the airport where a ‘‘suspicious package’’ — a phrase that has haunted this city since March 2 — was discovered. Police opened trucks and warehouse bay doors, examining packages for much of the morning.

Just a few hours earlier, a package bomb had exploded at a FedEx center in Schertz, Texas, 60 miles south of here. The package apparently was sent from a FedEx mailing office in north Austin and was addressed to someone in the city.

In a statement released Tuesday about the explosion in Schertz, FedEx said it had ‘‘confirmed that the individual responsible also shipped a second package that has now been secured and turned over to law enforcement.’’ An unexploded device could provide investigators with a trove of evidence.

Austin is going about its business, but in a cloud of uncertainty and fear as unfamiliar here as spring snow. Austin police have received more than 1,250 calls reporting suspicious packages in the past eight days. Recorded messages ring home phones with warnings of potential suspects in the area.

A columnist for the Austin American-Statesman on Tuesday compared the feeling in the city with the terror that gripped the Washington area in October 2002, when a pair of snipers randomly targeted residents for three weeks.

‘‘I found myself pondering the reality of soldiers in combat, of what it meant to know that at any time some unseen person could point a gun at you and pull the trigger,’’ wrote Ben Wear, who lived in Bethesda, Md., at the time.

The same rethinking of the world around them is happening among Austin residents, some of whom said their lives would forever change in small ways to accommodate the new reality. The bomber is using Austin’s particular vulnerabilities, its quirks and characteristics, to carry out a campaign that has stymied investigators.

Austin residents love their home-delivery services, such as Amazon and Instacart, a grocery chain that provides store-to-doorstep service. Residents can in some cases expect their orders within hours, and on most days, UPS and FedEx trucks are a common feature.

The first two bombs were delivered to doorsteps, including an early-morning package for 1112 Haverford Drive, where Anthony Stephan House lived, next to a home where two tiny bikes with training wheels were parked outside Tuesday.

The explosion, which blew out the front door and much of the entryway, sounded like a construction accident to Christin Hume, a photographer who was playing with her two dogs at the time of the blast.

‘‘We bought in this neighborhood because it was safe and quiet,’’ said Hume, 25, who lives five doors down from the bomb site with her husband, Chris, a software engineer.

The neighborhood east of Interstate 35 has changed, with young whites, Latinos, and South Asians joining a once-solidly African-American community. The houses are small and well kept, with many of them announcing that home-security systems are watching.

Investigators have said one theory is the attack on House was racially motivated. At the end of Haverford Drive, Chrystal Murray, 34, a payroll analyst at Apple, said she immediately had a similar thought.

Murray lives with her mother, who heard the early-morning blast. Once she was told the explosion killed an African-American up the street, Murray, who is black, said, ‘‘Race was then — and always is — a concern of mine.’’

‘‘There’s just so much hate right now,’’ she said, tracing the increase to the political climate since the 2016 presidential election. ‘‘But I guess that has been ruled out now. I just can’t believe people do stuff like this.’’

To the south, a different neighborhood, wealthier and whiter, is confronting the same questions and concerns.

Live oaks line the grassy median at the entrance of The Retreat at Travis Country, where playground equipment appears in almost every back yard and American flags hang from almost every portico.

Darkness had just fallen when two white men in their 20s rode their mountain bikes out of Gaines Creek Neighborhood Park. A box sat between the path and the sidewalk on a grassy strip. Invisible to the two men, a trip line joined the box to a yard sign. A bomb exploded, spraying nails. The two men were in good condition and recovering at a hospital.

When the bomb went off, Steve Bailey was traveling in Europe and Israel with his son. He heard about the attack from his wife, Angela, who was direct with the kids at home about what had happened.

The family and its neighbors have been wondering: Was the bomb meant for the children?

‘‘You have to question everything you do and have done until now,’’ Bailey said.

Material from the Associated Press was included in this report.