One of the three bodyguards of Dera Sacha Sauda chief Gurmeet Ram Rahim Singh -- arrested for killing a Sikh in Mumbai on Friday -- has confessed to having fired the round from his pistol at the crowd in, a senior police official said on Saturday.

He said Jagdev Singh Gurdev Singh has confessed to having opened fire from his licensed Mauser pistol.

Eleven more, who were with the Dera chief at the time of the incident have been detained and will be arrested soon, police said, adding they will be booked for rioting and assault.

"Now onwards, we will focus if the firing was in self defence or unprovoked," said the police officer.

Meanwhile, police suspect that one more person, apart from Jagdev Singh Gurdev Singh had fired as two empty shells of a 0.9 mm round were also found at the scene of crime on the Lal Bahadur Shastri Marg, he said, adding that forensic tests will ascertain the facts.

Reconstructing the sequence of events on Friday, the officer said two persons, including the deceased Balkar Singh Thakur Singh, got into a tiff with the Dera head's staff as they were not allowed entry into a shop.

Later, when the Dera chief left the mall in a motorcade, the duo's car happened to come near it after which some of the escort staff got down from their jeeps armed with sticks. They allegedly broke the windshield of Thakur's car and in the melee Gurudev Singh is suspected to have fired.