Flags flew at half-mast as Athens’s Paralympic Games ended on an emotional note after a school excursion bus collided with a truck on its way to the Games Monday, killing seven children and injuring many more, some of them seriously. The Athens 2004 Organizing Committee canceled the artistic program for the closing ceremony, and schools were closed on Wednesday, declared a day of mourning. Among the many telegrams of condolence sent to Greece was one to President Costis Stephanopoulos from his Russian counterpart Vladimir Putin, whose own country recently suffered the loss of many children killed in a raid after being held hostage in their school by Chechen rebels. The text of Putin’s message reads: “Your Excellency, It was with great sorrow that we heard of the terrible road accident that had such tragic consequences. We feel deeply for you in your sorrow and sympathize with the brother people of Greece. We know from experience how painful are the tragedies that take away from us what we hold most dear — the lives of our children. Please give my sincere personal condolences and those of the Russian people to the families of the victims and to all Greeks. V. Putin.”