Sebti saw a man bleeding from the chest and stooped to treat him when the second explosion occurred.

赛伯提看到一个男人的胸口正在流血，他就弯下腰去为他治疗，这时发生了第二次爆炸。

youdao

A message sent at 9.04am said that the fuselage of the first plane at the north tower had caused a second explosion - misinterpreting the second strike at the south tower.

上午9：04，一条发出的信息称，撞上北塔的飞机机身导致了引起了第二次爆炸——其实第二次是撞在了南塔上。

youdao

There is also a lake inside the second crater and the whole landscape reminds of the one after an explosion.

第二个火山口也有个湖，真个场面提醒着你这是火山喷发后的情景。

youdao

The explosion was the second at the same market in 10 days.

VOA: standard.2009.06.01

Running toward the finish line, Erik Savage turned and ducked when he heard the second explosion.

NPR: The Finish Line: What The Bombing Was Like

The second explosion happened metres from where a man was standing talking on his on mobile phone.

BBC: Pimlico pavement explodes, narrowly missing passer by

Most of the people were looking back at the first explosion, wondering what it was, when the second explosion went off.

WSJ: Two Explosions at Boston Marathon Finish Line