You would be amazed how bad the grammar is in newspapers, magazines, etc., written by native English speakers! These industries lose money every year, and they try to save costs by cutting jobs of editors, who in the past would correct these mistakes. I prefer your past perfect version of the sentence, because it is grammatically correct. However, native speakers often use a simple past form to describe both events happening in the past, and it is becoming more and more acceptable.

Hi Yancey, 雲小泉 is perfectly correct in pointing out that because the actions follow in the order they are reported, then past simple tense is correct. Past perfect is much more than "an order of events", and this is the biggest misunderstanding in its usage.

Witnesses said that there was nothing unusual before the explosion happened. There was nothing unusual before the explosion happened. This is correct. If you look at the sequence of events... 1. There was nothing. 2. The explosion happened. ...you will see that the use of the past simple is correct. You could however say: Before the explosion happened there had been nothing unusual. Remember, you use the past perfect when you describe an event that steps back further in the past. Another term for "past perfect" is in fact "the further past". I hope that helps.