It was a whole thing: https://en.wikipedia.org/wiki/Operation_Blue_Star

Operation Blue Star was a military operation by the Indian Armed Forces conducted between 1 and 10 June 1984 to remove Jarnail Singh Bhindranwale and other Sikh militants from the Golden Temple (Harmandir Sahib), a holy site of Sikhism, and its adjacent buildings.

The military underestimated the firepower possessed by the Sikh militants, whose armaments included Chinese-made rocket-propelled grenade launchers and ammunition with armour-piercing capabilities. Hoping to avoid damage to the holy site, Indian forces unsuccessfully assaulted the temple using light weaponry and quickly resorted to using heavy weapons, including tanks, helicopters and artillery to dislodge the well-fortified Sikh militants.

The assassination was at the back of this.