Born in 1962 in the Khan Yunis refugee camp in Gaza, Sinwar grew up in a family that originated from Al Majdal, near Ashkelon. He rose to prominence within Hamas from the group’s early days, co-founding its Majd unit, which targeted suspected collaborators with Israel.

Throughout his life, Sinwar was arrested multiple times and ultimately sentenced to five life terms for killing 12 Palestinians suspected of  collaborating with Israel.

During his imprisonment, Israeli doctors removed a tumor from Sinwar’s brain in 2007, saving his life.