On 15 September 1843, both Sher Singh and prime minister Dhian Singh were assassinated in a coup led by Ajit Singh Sandhawalia. However, the next day in a counter coup led by Dhian's son Hira Singh the assassins were killed. Aged 24, Hira Singh succeeded his father as prime minister, and installed the five-year old infant Duleep Singh as emperor. The Koh-i-noor was now fastened to the arm of the child emperor in court at Lahore. Duleep Singh and his mother empress Jind Kaur, had till then resided in Jammu, the kingdom governed by Gulab Singh.