snowleopard, as far as someone following him, parking quickly, and running up to shoot Dan--it comes down to a couple things. First, how long was it between Dan saying, "Someone is in my driveway," to the shot. If it was only a few seconds, then I think it means Dan was in his garage having just pulled in, he saw someone in one of his mirrors approaching his car, and then the shot was taken. In that case, I guess it's at least possible somebody followed him and when Dan pulled into the garage, the shooter pulled to the curb, and then came up the driveway for the shot.
However, if it was several seconds, like 15 seconds, I am more inclined to believe Dan saw the shooter before he pulled into his driveway. So Dan is out on the street, sees the shooter, makes the comment on the phone, pulls onto his driveway then into his garage, and the shooter follows him in. This would mean several more seconds between the statement and the shot.
But we don't know the timeframe between statement and shot so it's tough to say. The problem is at this point we don't know where Dan was when he said, "Someone is in my driveway." All it means is, well, someone was in his driveway--but we can't derive Dan's POV from that.
Also, when I hear someone say, "Someone is in my driveway," it sounds to me like Dan has no idea who the person is. This leads me to believe he didn't have any kind of road rage incident before coming home. It's not a certainty but at least a probability. If it were a road rage adversary, I would think Dan would've said, "The guy I almost ran into is in my driveway." You know what I mean? And I think he might've shown a little more apprehension in his voice. And to this point, it sounds to me like Dan said, "Someone is in my driveway," like any person would--with a bit of curiosity but no fear . . . yet. Once again, though, the only person who could judge Dan's demeanor in saying that sentence was the person he was talking to.
So, if he was followed, and it wasn't road rage, this goes back to the hired killer theory. Somebody might've staked out the school where Dan drops his kids off, and followed him to all those other spots before confronting Dan at his house at 11am. I guess it's possible. But with all the video cameras out there--ATM's, traffic lights, people's own home cameras, etc.--it's a bit of risk to follow a target for too long. Still possible, though.
Myself, I'm still leaning toward a person waiting at his home. <modsnip> I know we can't talk politics on here (for very good reasons) but I think Dan's shooting was politically motivated but not the way you might think. And it would fall into Razz's idea that the shooter was totally unhinged.