Four explosions have rocked Texas' capital in less than three weeks and authorities say a serial bomber is likely to blame. But they don't appear closer to making any arrests.
Three package bombs left on doorsteps over 10 days starting on March 2 killed two people and injured two others.
Then, on Sunday night, an explosive triggered by a nearly invisible tripwire wire injured two more.
Police originally pointed to possible hate crimes, but the victims have now been black, Hispanic and white and from different parts of the increasingly diverse city.
They looked for common threads among those hurt and killed, but now concede that a tripwire means who gets hit could be totally random.
Investigators were left with more questions than answers, as fear spread through Austin.
Australian Associated Press