Tunis attack

Members of the Tunisian armed forces take up positions during an operation against gunmen who opened fire on tourists at the National Bardo Museum in Tunis, Tunisia, on March 18.  (Mohamed Messara/EPA)

Tunisian President Beji Caid Essebsi, second from right, arrives at Charles Nicole Hospital to visit survivors of an attack at the Bardo Museum on March 18, 2015 in Tunis.  (Sofiene Hamdaoui, AFP/Getty Images)

Tourists are evacuated from the site of an attack carried out by two gunmen at Tunis’ famed National Bardo Museum on March 18, 2015.   (Salah Habibi, AFP/Getty Images)

Tunisian security forces open a gate for an ambulance carrying victims of a deadly attack at the National Bardo Museum on March 18, 2015.  (Fethi Belaid, AFP/Getty Images)

An injured person is evacuated from the National Bardo Museum, in Tunis, Tunisia, on March 18.  (Stringer/EPA)

A Tunisian security force helicopter flies over the site of an attack carried out by two gunmen at National Bardo Museum in Tunis on March 18, 2015.  (Salah Habibi, AFP/Getty Images)

Tunisian security clears the way for an ambulance carrying victims of an attack at the National Bardo Museum on March 18, 2015.  (Fethi Belaid, AFP/Getty Images)

A member of the Tunisian special security forces celebrates after two gunmen who attacked Tunis’ National Bardo Museum were killed on March 18, 2015.   (Fethi Belaid, AFP/Getty Images)

People flee the National Bardo Museum in Tunis during an attack by two men with assault rifles in a screen grab from the state-run Tunisia 1 channel on March 18, 2015.   (AFP/Getty Images)

A sniper of the Tunisian armed services walks past an armored vehicle during an operation against gunmen who opened fire on tourists at the National Bardo Museum, in Tunis, Tunisia, on March 18.  (Mohamed Messara/EPA)

Tunisian security forces search the grounds around the Bardo Museum after a deadly attack by two gunmen on March 18, 2015.  (Fethi Belaid, AFP/Getty Images)

A Tunisian nurse waits beside an ambulance for those injured when gunmen opened fire on tourists at the National Bardo Museum, in Tunis, Tunisia, on March 18.  (Mohamed Messara/EPA)

People at the National Bardo Museum in Tunis survey the aftermath of a deadly attack by two men armed with assault rifles in a screen grab taken from the state-run Tunisia 1 channel March 18, 2015.  (AFP/Getty Images)

Tunisian security forces near the National Bardo Museum in Tunis in the wake of the deadly attack by two gunmen on March 18, 2015.   (Fethi Belaid, AFP/Getty Images)