compound predicates: comma use when verbs share a subject
Two verbs with one subject.
Do not put a comma before the coordinating conjunction when two verbs share one subject: The train stopped and waited. Use the comma only when a second independent clause begins: The train stopped, and the guard waited.
Examples
UseShe filed the brief and left.
UseShe filed the brief, and the clerk left.
AvoidShe filed the brief, and left.