A lot of reddit posters live in basements, a subset of which are in the engineering building.

Most Reddit posters are children. What of it? How does "he was a Brown graduate who lived in the basement of the engineering building" follow?

Those two descriptions are not mutually contradictory.

What I heard is he called the police tip line and left a message but didn't hear back for two days. After two days he left this tip and then was made a person of interest. This is just what I heard, not sure if there's more to this story.

And...?? How does "he was a Brown graduate who lived in the basement of the engineering building" follow? Wtf?