Hey man, nice shot
When pumping gas you're in a position of relatively high vulnerability for theft, armed robbery, or attack.
First, you're standing outside of your vehicle, which is likely unlocked with the keys inside, making it an attractive and accessible target. All they have to do is get past you, which they may be able to achieve through speed, stealth, intimidation, or force.
Secondly, the layout of the gas station usually gives the perp multiple avenues of approach that are difficult for the target to see. Pumps, columns, and vehicles (including your own) all serve to block part of your view.
You can mitigate these risks through several means:
1) Carry a gun (or at least some weapon) and know how to use it. I start with this, because this is something you have to do before you leave the house. Better to have and not need than need and not have.
2) Consider locking your doors when you get out of the car and keeping the keys on your person. Even if you leave the driver door open, it means no one can gain entry to the vehicle through another door (overtly or covertly).
3) Keep your head on a swivel. If you don't see them coming, they get the drop on you, putting you at a major disadvantage. In this video the guy at the pump seems to notice the attacker pretty early on. This makes a huge difference. BONUS: If someone is walking straight towards you at a gas station, you should be on high alert. If they are dressed like the attacker in this video, you should take proactive measures (drawing your firearm, getting in the car, etc.)
Unlikely but possible scenario: One person approaches from one side as a distraction, while another person approaches from the exact opposite direction. This may seem counterintuitive, but as soon as you perceive a threat, if you have time, do a quick 360 degree look around to see if anything else pops up on your radar, but quickly re-orient towards the perceived threat. If you DO see someone approaching from behind, you need to act with speed and aggression:
1) If possible get in the car and drive off.
2) If (1) is not possible, see if you can move into a position where the threats are not on either side of you.
3) Pick a target to engage first. If they move from potential threat to active threat, engage with speed and aggression to neutralize the chosen target before transitioning to the second target.
Stay frosty out there.