Mor, who had over 5 lakh followers on TikTok and 3,000 followers on Instagram, was shot dead inside a photostat shop in Najafgarh on Tuesday.
The accused, 17, was arrested near Dhulsiras village in Dwarka. The juvenile was identified by call details records (CDR) as he was the last person to speak to the 27-year-old victim on the phone before the murder on May 14.
"A country made pistol and two live cartridges were recovered from his possession," said Sanjeev Kumar Yadav, Deputy Commissioner of Police (special cell), adding that his two accomplices, identified as Vikas and Rohit Malik, were still at large.
"The juvenile, Vikas and Rohit are part of a gang led by one Sandeep Pahalwan. A month back, the juvenile met Pahalwan and expressed his urge to join his gang following a personal enmity with someone. Pahalwan took him in on the condition that he would kill Mohit Mor," Yadav said.
"Pahalwan on Tuesday called the juvenile and asked him to meet him in Najafgarh. He later gave them three pistols, one each to the juvenile, Vikas and Rohit, and asked them to kill Mor either in the gym or in a photostat shop," the officer added.
"The accused persons found Mor sitting in a sofa inside the photostat shop and shot him dead after indiscriminately firing 14 rounds.
"During interrogation, the juvenile said that Mangu, an accomplice of Pahalwan who was killed earlier, had invested around Rs 30 lakh in a property in Mohan Garden through Mor. After the murder of Mangu, Mor refused to return the money to Pahalwan and instead took protection from the Manjeet Mahal gang," the DCP said.
"Few days back, Pahalwan had sent the juvenile to demand money from Mor, but the latter assaulted the juvenile after a fight broke out. Pahalwan, along with the juvenile and his two accomplices, then decided to eliminate Mor," another officer who is part of the investigation told .
The officer added that the juvenile called Mor on the phone and asked about his whereabouts to which the latter replied that he was at a shop in Najafgarh.
"A hunt is on to nab Pahalwan and the other two accused," the officer said.
( With inputs from IANS )