It could be because they anticipated a response that would target the university. But this announcement was particularly fast and early in the morning.
It's almost as if they knew ahead of time....or wanted their students to take part in the massacre.
The IUG has been a hotbed of terrorism for a long time. One of its founders was also a founder of Hamas, Sheikh Ahmed Yassin. In 2006, Jameela El Shanty, a professor there, said that "Hamas built this institution. The university presents the philosophy of Hamas. If you want to know what Hamas is, you can know it from the university."
Kidnapped Israeli soldier Gilad Shalit was held in captivity at the university for months.
Israel struck it early in the war because of its use as a Hamas stronghold.