What was behind the deadly Indonesian football match stampede?

Panic at an Indonesian football match after police fired tear gas to to disperse supporters invading the pitch left more than 170 people dead, mostly trampled to death, police said (Hendra Permana/AP)

Violence and a deadly stampede that erupted following a domestic league football match on Saturday night marked another tragedy in Indonesian football. Here is a look at how the chaos occurred and what is being done to prevent future incidents.

– How did the chaos occur?