Did Bourne purpously slow-walk out of the farmhouse after the explosion?

Think you're right. I mean, you would have a fairly good idea (if you were Bourne) how long it would take to acquire a target, reposition, aim, fire, so he does exactly that and starts sprinting just as the shot is fired.

Risky, but calculated risk.

I'm not so sure. I think he does it because he's using the explosion as cover and so doesn't have to run. He takes his time because the aftermath of the explosion takes several seconds to settle down. Once he is past that area, though, he then needs to run. Could be that running in that situation WOULD attract attention, which he doesn't want, because clearly the sniper would be focused on that area specifically for a few seconds.

Gosh, people, you really need to pay more attention before posting.

Go back to the beginning of that sequence (@ 1:24:00), a panorama of the farm property just as the kids are calling the dog. Notice the camera motion. That panorama is looking east from the hillside and it's Professor's view of the house as he squats with his sniper rifle in the woods on that hillside. We're looking through his scope. Also notice Eamon's red car. It's between the near side of the house and the corner of the wall where the propane tank is located. The car is in the driveway of course.

Now jump to Jason emerging through the front door (@1:26:16), rounding the far side of the house (far side from Professor's POV) where he shoots the propane tank (@1:26:22). He then walks down the front entry walk (not the gate beside the driveway through which he & Marie originally entered the property adjacent to the side door Jason busted through) and he doesn't run until he reaches the road.

When Jason shoots the propane tank, he's shooting almost directly in Professor's direction. To the right of the propane tank and slightly in front of it is a wood pile, and to the right of the wood pile, just to the right and slightly behind a tree, is the driveway gate, and beside that, the side gate through which Jason & Marie entered the property the previous day.

Why did Jason choose to go out the front door instead of the side door? He knows that the logical overlook an assassin would choose is the one on the side of the house near the driveway. How does he know that? Because it's where he would be if he were that assassin.

When Jason reaches the road, he goes through the neighbor's gate, again, on the far side of the house from where Professor is squatting. He's covered by the fire and smoke for most of the trip, He doesn't run until he has to.

All posts I've read in which critics claim to have found some small flaw in this film have proven to be simple cases of failure-to-pay-attention on the critic's part. I have not found a single flaw in this movie, and I have watched it over 20 times.

PS: I should add (to all would-be critics): Be cognizant of POV (point of view). Don't assume that every scene is from an omniscient POV. An omniscient POV is the easiest to use because it doesn't confuse viewers, but it has the least impact. Good films don't use omniscient POV, but use instead the POVs of protagonists and antagonists. In this case, we have the antagonist's POV.
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I don't have a dog. And furthermore, my dog doesn't bite. And furthermore, you provoked him.