Nigeria President Muhammadu Buhari, pictured at the White House in April 2018, called for calm and vowed to bring the perpetrators of Sunday's attack to justice. Bloomberg via Getty Images hide caption
Muhammadu Buhari
President Donald Trump meets with Nigerian President Muhammadu Buhari in the Oval Office of the White House on April 30. Olivier Douliery/Getty Images hide caption
A Nigerian man in Lagos reads a newspaper addressing President Mohammadu Buhari's "follow-up medical consultation" in London. Pius Utomi Ekpei/AFP/Getty Images hide caption
Nigerian President Muhammadu Buhari addresses members of his cabinet upon his arrival at the presidency last month in Abuja, Nigeria. Sunday Aghaeze/AFP/Getty Images hide caption