A test run? Yes, absolutely could be.
However, this shooter is damn lucky their license plate wasn't detected or they would have been caught by now.
Did they know there weren't any great surveillance cameras at the school?
Would you assume the cameras weren't that great? Either BRAZEN and BOLD and/or incredibly STUPID.
Not just a test run, but one done to ensure that the next morning SB would be in the company of others who could provide him a solid alibi at the time of his wife’s murder.
The husband would be among the first of those considered persons of interest based on statistics alone. So, IF the 2 am test run was done for the purpose of checking the time it would take SB to drive from home to Lowe’s, it may Indicate the killer wanted to ensure that it was easily provable SB was not in the vicinity. (Note that SB may have had no idea the killer was planning the murder and protecting him in this way as part of the plan.).
Who would have twin motivations to:
(1) put EB permanently out of the picture, AND
(2) protect SB from suspicion of involvement?
I could see only a few possibilities:
(1) someone who has a serious romantic interest in SB, or
(2) a close friend of SB’s who considers EB a poor mate for SB, or
(3) a close relative who considers EB a poor mate for SB.
But among those, who would have the means to place SB (or knowledge that SB would be placing himself) in the company of others who could vouch for his presence at that time of day?
Whose idea was it that SB meet others at Lowe’s before continuing on to work that morning? And if SB’s idea, who else knew about it?
SB meeting others at Lowe’s could have served two functions: (1) put SB in the presence of others who could vouch for his whereabouts at that time of day, and (2) keep SB away from the job site so SB would not know who was NOT at the job site (but typically would be) at that time of day.
The timing of the murder - very shortly after SB left, but before any garage sale shoppers show up, seems too precise to be presumed coincidental. I’d be very curious to know whether SB or those meeting SB at Lowe’s had any phone or text contact with anyone else around the time SB arrived at Lowe’s. (If SB or those he was meeting did have such contact, it may have been completely innocent on their part.)