A massive explosion obliterated a home in Pottstown, Pennsylvania, last week, killing five people — four children and an adult — and leaving the tight-knit community in shock. The explosion left a crater filled with gnarled metal and splintered lumber where a home once stood and many questions remain unanswered. Here’s what we know and don’t know. What happened? At around 8 p.m. Thursday, an explosion destroyed two houses and damaged at least six other houses. Neighbors described a thundering boom and said it felt like a bomb had gone off. Francine White, 67; Alana Wood, 13; Jeremiah White, 12…