A tour bus of US senior citizens defended themselves against a group of alleged muggers, sending two of them fleeing and killing a third in the Atlantic coast city of Limon, Costa Rica police said on Thursday. One of the tourists - a retired member of the US military - put assailant Warner Segura in a head lock and broke his clavicle after the 20-year-old and two other men armed with a knife and gun held up their tour bus Wednesday, said Luis Hernandez, the police chief of Limon, 130 kilometers (80 miles) east of San Jose. The two other men fled when the 12 senior citizens started defending themselves. The tourists then drove Segura to the Red Cross where the man was declared dead. The Red Cross also treated one of the tourists for an anxiety attack, Hernandez said.