US President Barack Obama called Sunday for Americans to keep calm after a jury acquitted George Zimmerman in the killing of unarmed black teenager Trayvon Martin. "The death of Trayvon Martin was a tragedy. Not just for his family, or for any one community, but for America," said Obama, who first weighed in on the case shortly after the killing last year by noting that if he had had a son that the child would "look like Trayvon." The president acknowledged in a statement that the case had "elicited strong passions," but noted that "we are a nation of laws and jury has spoken" and called for calm reactions in the wake of the verdict, according to a report of DPA. "We should ask ourselves, as individuals and as a society, how we can prevent future tragedies like this. As citizens, that's a job for all of us. That's the way to honor Trayvon Martin," he said, calling on Americans to reflect on ways to prevent further gun violence and broaden understanding.