Looking over a few bits and pieces, I've drawn a tentative conclusion that the sniper is the Von Helsons Father - Vlad.

I have two reasons for this (they both can be linked together so I'll put them here).

1. The Sniper shoots Gambino because of the threat he's posing to the Von Helson twins - he does not anticipate the tower falling onto Durem.

(Based on my idea that Gambino's mother is actually the twins Mother - making him not only the Gambino heir, but the Von Helson one as well -if you go by traditional father to son generations)

**1a. The Sniper is not only protecting the Twins, but Gino who's just got his memory back - a blank canvas is easier to achieve the desired results after all.

2 - The Sniper shoots Ian because he knows that the constant fighting for Sasha's affections is bringing out more of Gambino's genes in Gino and that would mean the return of a strong Gambino family, something the weakened Von Helsons would not want to see.

**2a. The Sniper shoots Ian because he's protecting Gino's interest in Sasha, ensuring that an heir is possible.

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3. The Sniper shoots at Edmund because he's becoming a threat to the rise and return of the illustrious Von Helsons!

What say you people?

AND, all three shots have been taken in Durem - the place where the Von Helson manner is based.
The figure of the sniper is out in daylight - but wrapped in heavy black fabric; and since no one is looking up at the tower, or going to investigate after the shot - there MUST be another reason for the all covering protective clothes!