The blast was caused by a tripwire, which Police Chief Brian Manley said demonstrates a "higher level of sophistication" than previous package bombs. Manley said the tripwire design required a higher level of skill to construct and represents a "significant change." A tripwire is a victim-operated switch that uses some kind of wire that's attached to an explosive device. What material was used in the latest Austin device? Milanowski said the latest explosive device was anchored to a metal yard sign near the head of a hiking trail in Travis Country.

Source: Fox News March 19, 2018 20:25 UTC