Kenyan President Uhuru Kenyatta declared on Tuesday that the four-day long attack, involving Al-Shabaab terrorists, on a mall in Nairobi has ended.

According to BBC News, five of the attackers were shot dead, and the remaining 11 are in custody. Kenyatta has declared three days of national mourning, beginning tomorrow, for the 61 civilians and six soldiers killed in the attack. The death toll is expected to rise, however, as more bodies are recovered from the mall, where the floor has collapsed, The Washington Post reports.

Kenyan Foreign Minister Amina Mohamed said on Monday that “two or three Americans,” those members of the Al-Shabaab American branch, were involved in the attack, but it is not yet known whether this is true. Kenyatta assured that experts, through forensic tests, would determine whether or not any Americans were among the attackers.

This attack could have long-lasting impacts worldwide. Experts told FOX News that soft targets in the US, such as shopping malls and sports arenas, should increase security and update emergency response plans. Bill Nesbitt, president of California’s Security Management Services International Inc., said that it was not unreasonable to increase security in light of the attack in Nairobi, and warned that there is a possibility of a copycat attack.