The border crossing was closed Sunday in an effort to prevent the assassin or assassins from leaving Gaza. The Rafah border crossing with Egypt also reportedly has been closed by Hamas.

Thousands attended the funeral for Mazan Fukha in Gaza on Saturday, which was attended by Hamas senior official Ismail Haniyeh, Ynet reported.

Fukha was assassinated on Friday night outside of his Gaza home, according to reports. Hamas is blaming Israel’s Mossad for his death. Mourners shouted “revenge” against Israel during the funeral, the AFP news agency reported.

The Israeli side of the Erez crossing, the only place where people cross in and out of Gaza, will remain open. The Kerem Shalom crossing, which is used for goods and humanitarian aid, also will remain open, according to Israeli officials.

Fukha, who Israel says founded Hamas in the West Bank and helped coordinate terror attacks against Israelis, was jailed in Israel after being found responsible for suicide attacks that killed hundreds of Israelis during the second Intifada.

He was released from prison in Israel in 2011, as part of the Gilad Shalit prisoner exchange and ordered deported to Gaza.