Why does Paris attack romeo at the Capulet tomb?

Paris does not actually fight Romeo at the tomb. He arrives at Juliet's tomb during Romeo and Juliet's final scene, and he mistakes Romeo's mourning for her as a show of defiance. He believes Romeo has trespassed on private property and tries to intervene. The two have a brief verbal disagreement before Romeo urges him to leave. However, Romeo does not attack Paris physically.