The case was transferred to CBI from Delhi Police for further investigation after the victim's parents met Union home minister Sushilkumar Shinde and Congress vice-president Rahul Gandhi, demanding speedy justice for Tania (also spelt as Taniam).
They had alleged police negligence in the case and also demanded action against the guilty personnel.
The accused were apprehended after relatives of Tania, a BA first year student in a private university, alleged that he had an altercation with some shopkeepers at Lajpat Nagar market here on January 29 after they made fun of his hair style. Following the altercation shopkeepers had allegedly thrashed him. He was brought dead to AIIMS the next day.
The death of Tania, son of a Congress MLA, evoked angry reactions from people of the northeast living in the national capital who alleged police had failed to protect him.
Police had booked all the four under Section 302 (murder) of IPC after the postmortem report revealed that Tania died due to injuries to his head and face caused by a blunt object.
Initially, police had on February 3 arrested three of the accused under the Scheduled Castes and Scheduled Tribes (SC/ST) (Prevention of Atrocities) Act, 1989.
On February 10, police arrested Sunny and slapped murder charge on all the four accused. Two minors who also allegedly assaulted Tania are facing an inquiry before the Juvenile Justice Board here.