美国有线新闻 CNN 美国奥斯汀连发爆炸案 市民陷入恐慌（在线收听）

AZUZ: Police in Austin, the capital of Texas, are telling people to call them if they see anything suspicious and they're offering a reward of $115,000. It's because they think a serial bomber may be on the loose.

For the fourth time this month, an explosive device has go?ne off in the city. The previous three explosions came from packages left on people's doorsteps. But what happened Sunday night involved the device that was placed on the side of the road and triggered by a tripwire when two men walked by. They were hurt but they're expected to recover. Two of the victims from the other bombings died.

Police say the tripwire bomb was more sophisticated than the others, indicating the bomber might have some sort of explosives training. The bombs were placed or sent to different parts of the city and as you'd expect, residents across Austin are on edge. Even a bomb threat made on Saturday caused the cancellation of a concert at the South by Southwest Music Festival. In that case, officers didn't find any explosives, but because of the other ones, police say people need to avoid anything that looks out of place, and they're asking for those who have security camera footage to contact police immediately.