Law enforcement officials are just beginning the process of tracking down the person or persons  responsible for Monday's bombing that left more than 170 people injured and three dead near the finish line of the Boston Marathon.Boston Police Commissioner Ed Davis said today no one is in custody and he is making a plea  to the public to turn in any photographic or digital evidence they have from the scene. "There have to be thousands of photographs or videos or observations that were made at the finish line yesterday" And law enforcement officials are asking everyone to bring them forward so they can be reviewed.Anyone with any information is asked to call 1-800-494-TIPS.