jones shot and killed shacar wingate on saturday night. police found wingate's body in edgewood. >>> american officials have released a warning for all american tourists. >> reporter: the u.s. state department issued an alert sunday urging americans to take caution when traveling in europe. the alert warns of a potential terror plot that could target popular tourist destinations and mass transit hubs. >> make sure that you've registered with the american agency. if you avoid public demonstrations, avoid civil disturbances. >> reporter: the alert is one step below a formal travel warning. which would advise americans not to visit europe. it marks the first time in recent history the state department has issued an alert for an entire continent because of a security threat. over seas, the news put some american tourists on edge. >> coming to madrid has put me kind of an edge a little bit to be aware and kind of watch out for things. >> reporter: intelligence officials believe osama bin laden may be behind the plot to attack several cities in