Chhattisgarh CM Bhupesh Baghel was meanwhile prevented from leaving the Lucknow airport to enter Uttar Pradesh where he said he wished to meet Priyanka Gandhi Vadra.
Protests at the site of the incident have eased after Rakesh Tikait's intervention.
The two firebrand politicians, who have significant pasts as Leftist leaders, appear to be significant inductions as Rahul Gandhi steers Congress far from leaders keen on displaying 'soft Hindutva' politics.
The killing of 45-year-old Vipin Agarwal is not a one-off incident, for as many as 20 RTI activists have been murdered in the state since 2006.
As the 'super CM', Sidhu holds the reins of the Punjab government and Congress party, evident from the composition of the new Cabinet. However, emerging caste politics in the state could harm his political ambitions.