The mob wanted to get Pappu Yadav hanged as soon as he was arrested.
The Police took him to the Outpost in order to protect him from the mob.
Because a mob is dangerous.
When almost 200 people of the same caste attack one man,
then what option does the Constable have?
The Constable will try to protect the man,
take him inside and get his side of the story and
inform his superiors.