Why was David Headley fatally attacked?

"Daood Sayed Gilani, one of the plotters of the 26/11 attack was an american with an pakistani origin.. Daood also famously known as David Coleman Headley lived with his parents in Philadelphia. David, since 2002, started his introductory course with the LeT and within a span of time Saeed became Headley's new handler which ended up with his role in 26/11 attack. He was later sentenced to 35 years in prison by the US court in which more than 160 people were killed. And now the killer of multiple innocent people is battling for his own life in the ICU at Chicago. As he was being attacked by his prison inmates. So what could be the possible reasons why he could be attacked? The Indian government was seeking extradition of David Headley to stand trial for his involvement in 26/11 Mumbai attack. Looking at his current critical state this extradition looks unlikely that he would recover.