witnessing something first-hand in real life, and then reading about it in the media
You don't even need to read about it elsewhere. Your own recollection of the details of events you witnessed is usually very malleable. It's one reason why eyewitness testimony needs to be treated carefully. E.g. from Wikipedia[1]:
Memory recall has been considered a credible
source in the past, but has recently come under
attack as forensics can now support psychologists
in their claim that memories and individual
perceptions are unreliable; being easily
manipulated, altered, and biased.
You don't even need to read about it elsewhere. Your own recollection of the details of events you witnessed is usually very malleable. It's one reason why eyewitness testimony needs to be treated carefully. E.g. from Wikipedia[1]:
[1] https://en.wikipedia.org/wiki/Eyewitness_testimony