Formerly a member of anti-Shia militant group Sipah-e-Sahaba, Ishaq co-founded the LeJ in 1996. Under Ishaq's leadership, the LeJ claimed responsibility for several mass-casualty attacks largely targeting Pakistan's Shia and Barelvi population, including multiple bombings that killed over 200 Hazara Shias in Quetta in 2013. He was also accused of masterminding the attack on the Sri Lankan cricket team in Lahore in 2009, and the Ashura bombings in Afghanistan in 2011.