He noticed the men, who were presumed to be Secret Service Agents riding in the car directly behind the President's car, unloading from the car, some with firearms in their hands, and noticed police officers and these plain clothes-men running up the grassy slope across Elm Street from his location and toward a wooded and bushy area located cross Elm Street from him... Because of this activity he presumed the shots which were fired came from the shrubbery or bushes toward which these officers appeared to be running.