The Somalia terrorist group Al-Shabab has named a new leader to replace Ahmed Abdi Godane, the top commander killed in a U.S. airstrike last week. Sheikh Ahmad Umar, aka Abu Abaidah, will become the al Qaeda wing’s third leader, the group announced Saturday.

The Islamist extremists also pledged to take revenge for the death of one of its founding members, Al-Jazeera reported. “Avenging the death of our scholars and leaders is a binding obligation on our shoulders that we will never relinquish nor forget no matter how long it takes,” the group said in a statement sent to the news organization.

Godane had led the group since 2008, after its first commander, Ismail Arale, was sent to Guantanamo Bay. Godane masterminded a number of attacks on civilians, including the 2013 shootings in the Westgate shopping mall in Nairobi, Kenya, that killed 63 people. He also led Al-Shabab’s fight against U.S.-backed troops in Somalia. The group controlled the capital, Mogadishu, from 2006 to 2011, when it was driven out by an African Union peacekeeping force.

Godane was in south-central Somalia when he was hit by Hellfire missiles and laser-guided munitions Monday, Reuters said. However, the Pentagon did not confirm his death until Friday. “Removing Godane from the battlefield is a major symbolic and operational loss to Al-Shabab,” Rear Adm. John Kirby, the Pentagon press secretary, said in a statement.