Tunisia's prime minister fired five police commanders Monday in the wake of last week's terrorist assault in Tunis on the country's national museum that left 21 people dead -- all but one of them foreign tourists. Habib Essid fired the head of tourist security, an intelligence brigade chief, the Tunis police chief and two others. His spokesman said Essid visited the National Bardo Museum on Sunday and found "several security failures." Tunisian authorities say guards assigned to provide security at the museum and the adjacent parliament complex were having coffee at the time two militants gunned down the tourists, including visitors from Japan, Poland, Italy and Spain, as they got off buses at the museum. The two gunmen rampaged through the museum for hours last Wednesday before they eventually were killed by security forces. The militants were later identified as two Tunisians in their 20's who had trained in Libya. Tunisian President Beji Caid Essebsi said Sunday that a third gunman linked to the massacre is on the loose. "Two were executed but one is on the run still; but, he won't go very far," Essebsi told French television interviewers from inside the museum. Tunisia's Interior Ministry released security camera video showing two men armed with assault rifles walking through the museum. At one point, they encounter a third man with a backpack, briefly acknowledge each other, and then head in opposite directions. Essebsi said, "The police and intelligence were not systematic enough to ensure the safety of the museum." Islamic State militants, who are seeking to establish a caliphate across Iraq, Syria and other parts of the Muslim world, claimed responsibility for the attack, but purported details also have appeared on social media sites linked to an al-Qaida-affiliated group in Tunisia.