Bob F asks in comments:
Somewhat related: I have been skeptical of the term "person of interest" since I first heard it. My suspicious mind has always said it was an end run around legalities when a person is officially considered a suspect, the word "suspect" carrying certain obligations. If you would care to opine at some point down the road I'd definitely be interested in learning.
It's simple. A suspect is someone suspected of a crime. Why might we suspect that a particular person did a particular crime? In this day and age, we have video camera everywhere. Almost any violent crime a person ight commit is generally captured on a video camera of some type.
Back in the day it was a little harder. For example, in the early to mid 80s I was an investigator, and I got to know the methods used by a certain portion of my criminal element. There was one career burglar who always went in through the bedroom window, left the screen propped against the house, and always left through the front door. He stole things that were easy to carry and easy to hock. If I saw that set of circumstances at a crime scene, I knew who my suspect was. He was a guy named Deadeye. Deadeye always committed burglaries the same way.
A person of interest is not the suspect. A person if interest is a person who might know the whereabouts of my suspect. For example, in Deadeye's case, my person of interest was Jerry Wayne. Jerry Wayne always knew where I might find Deadeye.
In the current case, the cops were looking for a particular Jeep Cherokee. They knew it was used in the murder of my friend, and they suspected that the vehicle might have evidence inside it. When they found the car, and stopped it in a traffic stop, the fellow driving it became a person of interest. As i turns our, he was arrested as and Accessory After The Fact.
As it turns out, I never personally arrested Jerry Wayne, my person of interest. I arrested Deadeye several times over 20 years and the last I heard from him, he is living in his mother's house and staying out of trouble. Jerry Wayne died in the early 90s. Something about a drug deal gone bad and a bullet in his head.I don't know if they ever solved that one.