I’m not.

He legally owned a white Elantra. Immutable fact, not a crime on its own. That would be available data to authorities per DMV records, car registration, insurance, taxes, university parking registration, etc.

That puts him in a (large) suspect pool of all white Elantra owners in a tri-state area, since that was of interest to LE due to its connection to the time and place of the crime scene.

If he were to sell his vehicle or destroy his vehicle when LE is publicly searching for the white Elantra, that would then put him in a much narrower suspect pool of maybe the 40 some odd white Elantra owners in a tri-state area who conduct a vehicle transaction or sell their white Elantra in the six-month or whatever time period after the crime is committed. Selling a vehicle or buying a new one generates a paper trail, or rather a digital trail, which can trigger additional scrutiny on people already in a broad suspect pool. Not enough on its own though.

No clue how the authorities figured out this guy did it, looking forward to seeing how they cracked the case, but that would be a logical reason why this sociopathic criminal science person may have thought to keep the car and act normal. May also already have incriminated himself from the outset due to traffic cameras and available public records, so I’m sure law enforcement was seeking additional concrete evidence to tie this dude to the specific crime. There’s a whole legal process to discovery and how to build a case to lead to arrest to lead to prosecution, so I’m sure they were being very careful.