Q: "People heading home from work at the train station." Does this mean that "People are going home."?
A: yes

Q: "A man in a blue shirt holds up a protest sign." Does this mean that "A man holds a protest sign"?
A: it is not possible to tell

Q: "A group of people gathering outside." Does this mean that "A group of reporters wait for the verdict outside the courthouse."?
A: it is not possible to tell

Q: "A security person in lime green monitors the busy city streets." Does this mean that "The security person watches a car run a red light."?
A:
yes