Information after an event travels in a progression from
primary sources: “I was there” (diaries, letters, posters, photos, etc) to:
secondary sources: “I wasn’t there, but I am talking to or reading about someone who was there” (magazines, newspapers, books).
Scholarly sources: “I study primary sources to understand what happened" (peer reviewed journals, etc)
Tertiary sources “We have studied this event and are writing to give you an overview of what happened and the effects afterwards” (encyclopedias, subject series, etc).
Items that were written at the time of the event such as newspapers are secondary sources at that point...but can become primary sources later as researchers study the newspaper as a product of its time.