Terming the incident as serious, Chief Minister Yogi Adityanath has ordered a probe.
Four jail officials have been suspended in connection with the incident.
Additional Director General, Prisons, Chandra Prakash said that Bajrangi (51) was kept in a cell with 10 other inmates including Sunil Rathi, who is also a gangster and lodged in Baghpat Jail since July 31 last year.
"Rathi shot Bajrangi after they entered into an altercation this morning inside the jail," the ADG said adding that Rathi has been taken into police custody.
Bajrangi was brought here from Jhansi Jail yesterday and was to be produced in a local court today in a case of demanding extortion money from BJP MLA Lokesh Dixit in 2017.
"More than one shot was fired. After the incident, Rathi threw the weapon in a sewer. We are probing how the weapon reached the jail," the SP said.
Principal Secretary, Home, Arvind Kumar said Jailor, Udai Pratap Singh, Deputy Jailor, Shivaji Yadav, Head Warden, Arjinder Singh and Warden, Madhav Kumar, have been suspended in connection with the incident.
A probe by a judicial magistrate will be undertaken as per procedure, he said and added that an FIR has been lodged in the matter.
On June 29, Bajrangi's wife Seema Singh held a press conference in which she alleged that her husband's life was in danger.
Bajrangi, who was accused in as many as 40 criminal cases including that of murder and extortion had contested the 2012 Assembly polls from Madiyahu seat in Jaunpur on an Apna Dal ticket.
In March 2016, Bajrangi's brother-in-law Pushpjeet, who looked after his business, was shot dead in Vikas Nagar colony of Lucknow and his close associate Tariq was shot at in Lucknow in December last year.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)