Germany's Dominik Koepfer, right, congratulates Switzerland's Stan Wawrinka with his win in the second round match of the French Open tennis tournament at the Roland Garros stadium in Paris, France, Wednesday, Sept. 30, 2020. (AP Photo/Alessandra Tarantino)PARIS – A tennis player at the French Open was visibly startled by a sonic boom Wednesday just as he was about to serve a ball. But with no forewarning, residents around Paris — along with fans and players inside Roland Garros — expressed their fears of an explosion on social networks. On Court Suzanne Lenglen, the second-biggest stadium at the French Open, Dominik Koepfer was interrupted mid-serve by the bang's loud clap. "It was a weird feeling, for one or two points I thought about it.”Wawrinka, the 2015 French Open champion, quickly sought to find out what happened.