Speculation in this matter is bad, but keep in mind too that concussions are a weird beast. Obviously Jamar made a mistake by driving away, but at the same time, he may not have really made a conscious decision to drive away. From Webmd.com on the symptoms of a concussion:
Symptoms of a concussion include:
Passing out.
Not being able to remember what happened after the injury.
Acting confused, asking the same question over and over, slurring words, or not being able to concentrate.
Feeling lightheaded, seeing "stars," having blurry vision, or experiencing ringing in the ears.
Not being able to stand or walk; or having coordination and balance problems.
Feeling nauseated or throwing up.
I've also talked to people before that have gotten concussions playing sports or something, not thought anything of it, kept playing, then suddenly felt strange and not remembered that they had continued to play. It's possible that Jamar was drunk and fled from the scene because he was afraid. It's also possible that he was not thinking clearly at all and acted with only the best intensions. We don't know, I'm just glad it looks like everybody is going to be ok.