Sinwar was born in the Khan Younis refugee camp in 1975 and was first arrested for militant activities as a teenager. He became the leader of Hamas’ Khan Younis brigade and is said to have played a key role in the Hamas operation that captured Israeli soldier Gilad Shalit in 2006, according to the Counter Extremism Project, and in insisting on his brother’s release from an Israeli prison in return for Shalit’s freedom.