The gun-wielding man, who shot at protesters outside Jamia Millia Islamia, went live on Facebook at least four times minutes before opening fire on Thursday.
The 19-year-old attacker had been seemingly planning the attack since the past week, his Facebook posts indicate.
His account has been now taken down from Facebook.
In one of his posts on January 28, the attacker had asked his over 3,000 Facebook friends not to "ignore his updates" till January 31.
Even on Thursday, he kept live-streaming from the spot where he later opened fire.
His posts were widely shared and generated considerable response. After he opened fire on Thursday, some of his followers congratulated and lauded him for the attack.
Since January 28, his posts referred to Shaheen Bagh and Hindutva.
One of his posts earlier Thursday read: "Shaheen Bagh Khel Khatam, (Shaheen Bagh, game over)."
The attacker was caught on camera shouting "Yeh Lo Aazadi" and brandishing a gun at Jamia students who were taking out a march against Citizenship Amendment Act and NRC. The event took place in the presence of media and a huge contingent of police.
In another post, the gunman wrote there is "no Hindu media here."
His posts also suggest that he was anticipating some action against him for what he had planned. For instance, before he went live on Facebook, the gunman urged his supporters to drape him in a saffron flag and chant "Jai Sri Ram" on his last journey.
While it is yet to be ascertained whether the gunman is associated with any outfit, a post on timeline suggests that Thursday's act was carried out of vengeance.
The armed man also urged people not to call him while he was doing live.
"Chandan Bhai Ye Badla Aapke Liye (Chandan bhai, all this for you)", one of his posts reads.
On January 26, 2018, Chandan Gupta, a 22-year-old, boy was killed during a Tiranga Yatra in Uttar Pradesh's Kasganj.
The gunman, a residnet of Greater Noida's Jewar, was later overpowered and arrested by Delhi Police and taken for questioning.
