Austin on edge after fourth bombing injures two people

AUSTIN, Texas - Richard Herrington was near the window in his television room Sunday night when he heard a sound in the distance that took him back to his Army days: the "distinctive thump" of a mortar detonating.

His first thought: "It's the bomber."

He was right. The explosion was the fourth in a series of attacks this month that authorities believe are connected - and have many in the Texas capital feeling terrorized. But the latest blast came with two twists that have increased anxiety here, and forced authorities to reconsider some of their hunches in the investigation.

While the earlier devices were package bombs placed on doorsteps, this bomb was apparently set for random passersby, employing a tripwire that police said demonstrated a "higher level of sophistication."

And the