MALANG, Indonesia—When the tear gas got to Hutriadi Hermanto and his friend Faris Brahmanto in the stands of an Indonesian soccer game earlier this month, it hit them hard. Mr. Faris said he felt like he couldn’t breathe. A large crowd had already gathered on the staircase that descended to the exit. There was pushing and shoving, and people were falling down. Some leapt over others to the front, or stepped on arms, legs, chests to make it out alive.

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