why did it take place?
Because of the Huế Phật Đản shootings.
Background
The incident occurred during a period of popular unrest by the Buddhist majority against the Roman Catholic rule of Diệm. Buddhist discontent had grown since the Huế Phật Đản shootings on May 8, 1963.
what is the double seven day scuffle? A physical altercation on July 7, 1963. between who? The secret police of Ngô Đình Nhu—the brother of President Ngô Đình Diệm—and a group of US journalists. who was arrested? Browne and Arnett. who was interrogated? Browne and Arnett.
US journalists were covering protests held by Buddhists on the ninth anniversary of Diệm's rise to power. American pressmen had been alerted to an upcoming Buddhist demonstration to coincide with Double Seven Day, the Buddhist monks were blocked, but they did not resist, but Arnett and Browne began taking photos of the confrontation. The police thereupon punched Arnett in the nose Arnett and Browne began taking photos of the confrontation. The police, who were loyal to Ngo Dinh Nhu, thereupon punched Arnett in the nose leading to a scuffle
Double Seven Day scuffle Double Seven Day scuffle Double Seven Day scuffle
Introduction Incident Incident
f US journalists who were covering protests held by Buddhists on the ninth anniversary of Diệm's rise to power. American pressmen had been alerted to an upcoming Buddhist demonstration to coincide with Double Seven Day at Chanatareansey Pagoda in the north of Saigon. The nine-man group, which included Arnett, Browne, AP photographer Horst Faas, David Halberstam, Neil Sheehan of "United Press International", and CBS's Peter Kalischer and photographer Joseph Masraf waited outside the building with their equipment. After an hour-long religious ceremony, the Buddhist monks, numbering around 300, filed out of the pagoda into a narrow alley along a side street, where they were blocked and ordered to stop by plain-clothed policemen. The Buddhists did not resist, but Arnett and Browne began taking photos of the confrontation. The police, who were loyal to Ngo Dinh Nhu, thereupon punched Arnett in the nose, knocked him to the ground, kicked him with their pointed-toe shoes, and broke his camera. Halberstam, who won a Pulitzer Prize for his coverage of the Buddhist crisis, was a tall man, standing around  Arnett and Browne began taking photos of the confrontation. The police, who were loyal to Ngo Dinh Nhu, thereupon punched Arnett in the nose, knocked him to the ground, kicked him with their pointed-toe shoes, and broke his camera. Halberstam, who won a Pulitzer Prize for his coverage of the Buddhist crisis, was a tall man, standing around taller than the average Vietnamese policeman. 
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Double Seven Day scuffle [SEP] Background
The incident occurred during a period of popular unrest by the Buddhist majority against the Roman Catholic rule of Diệm. Buddhist discontent had grown since the Huế Phật Đản shootings on May 8, 1963. The government decided to selectively invoke a law, prohibiting the display of religious flags, by banning the use of the Buddhist flag on Vesak, the birthday of Gautama Buddha. One week earlier, the Vatican flag had been flown at a celebration for Archbishop Ngô Đình Thục, Diệm's brother. The Buddhists defied the ban, flying their flags on Vesak and holding a demonstration, which was ended with government gunfire and eight or nine deaths.