There are just so many possible angles here. I don't think it was a professional hit (I could be wrong, of course). I do believe it was done in a fit of rage, but not road rage.
1.) Angry student: I can imagine an angry student because someone with certain forms of M.I. don't think rationally. There was a student in a Nutrition class I took who was always arguing with the professor. The prof was as nice as could be, and I think the student tried to take advantage of the prof's good nature, but the prof was firm in his responses. Some of the other students would even upbraid the angry student. I was afraid that would make him angrier, and this was way before hearing about any of the mass school shootings. Nothing seemed to quell this student, and I got the sense he didn't do well at all in the class since he would argue with the prof on almost every single question when we went over an exam. Yes, it seems to me that there has been sufficient time for an angry student to simmer down following the end of the semester, but someone with a persecution complex/paranoia could have been plotting over the past few weeks, following Markel to learn his schedule.
2.) Markel's consulting work involving the Rabbis is a new angle, but remote possibility.
3.) What I am leaning toward is Markel's death being related to his divorce. Of course, those closest to Markel such as an ex-wife will be investigated thoroughly first. But, as someone already mentioned, it could be a relative of the wife who carried out the plot without her knowledge. I will have to look up the article, but IIRC one of the points of contention in the messy divorce were some family heirlooms. Was Markel still in possession of some valuable heirlooms that his in-laws felt rightfully belonged in their family? It does seem that the perp was familiar with Markel's schedule. Did he/she confront Dan somewhere earlier that day?
Posters have been saying that they don't believe two cars could fit in Markel's garage and so think that the Prius was parked on the street. I couldn't find a website that tells whether the garage at that address is a one-car or two-car, but homes.findthebest.com shows that the garage is 550 sq. ft. I searched the web for the standard size of a two-car garage, and it is 400 sq. ft. So, two cars could definitely fit in that garage. I've also noticed in the picture of the house that the drive broadens at the top of the drive in a turn-around. I'm wondering if the Prius was parked in that spot on the right side and maybe the driver hid behind the shrub on the right side of the house, or more likely in the recess to the left of the garage where there are more shrubs. Then the person could easy run out as soon as Dan pulled into the garage, and approach him on the driver's side. And then they could quickly reach their car and drive away. I think the person wanted to do the job and flee swiftly while avoiding attracting much attention, and thought one shot to the head at close range would certainly be sufficient.
http://homes.findthebest.com/l/78552264/2116-Trescott-Dr-Tallahassee-FL-32308
http://www.ehow.com/facts_7166797_average-size-two_car-garage.html
