Hardeep Singh Nijjar, a pro-Khalistan leader living in Canada, was shot dead at the Guru Nanak Sikh Gurdwara in Surrey, British Columbia.
He was the president of Surrey's Guru Nanak Sikh Gurdwara.
Nijjar was affiliated with the outlawed separatist movement Sikhs for Justice (SFJ).
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He was instrumental in planning the Khalistan referendum in Brampton.
The National Investigation Agency had already filed a charge sheet against Nijjar for allegedly plotting terrorist acts.
India has requested that Canadian authorities prosecute Nijjar for his suspected participation in terrorist actions in Punjab.