In my view, after struggling to position his car in the road, it would take him only about 30 seconds to pass from camera view to park, and then a 30 second sprint to the back deck. 1 minute, not "minutes." But then I believe he mentally and physically trained and practiced. Why would it take "a few minutes" to drive 30 yards and park? It looks from where police were studying track marks that he parked at the very edge of their parking lot.
Why does it take 2 minutes to pick up his knife? Why isn't it already in his jacket pocket or on the seat of the car? He ought to have left the sheath in the car, obviously, but didn't even do that. Just grabbed it and ran into the house, pumping himself up on adrenalin and activating his muscles.
Why does he walk to the house? This is a man who is said to go on frequent 6-7 mile runs. His whole goal is doing this quickly.
In Marine Corps training, I'm told by marines here and in real life that 15 seconds is the goal they work for, in learning how to use that knife as an offensive killing device. 15 seconds to kill each person (in terms of the actual use of the knife).
I think it's hard for all of us to realize that this maniac psyched himself up into this killing state, which he had anticipated and fantasized about for months or years. He had certain goals and inward "personal best" records to satisfy. His mind was sharp and focused at the time. He believed himself to be in fine rational form and even better physical fitness.
That's why he thought he'd get away from it. But, as the maxim in criminology goes, he left something there (the sheath) and picked something up (blood on his shoes) He probably also left touch DNA here and there, and there was likely more blood than just blood on one shoe (on his person).
Since he left so quickly, I think he just jumped in the car and peeled out, so I'm hopeful there will be victim DNA in the car.