@nousernames
Not that I know of, sorry. The official translated version on Kindle might have it but don’t know if there’s a website that scans the tankobon releases.
Might be a bit of a spoiler? But since I saw comments in ch. 264 that were worried about the fact that ; added scenes in the Tankobon show that it was probably . .
@MRain
There's added flashback scenes in the Tankobon when Koito and co. meet up with Tsurumi to hand over Asripa. It's clarified there that it was a handgun bullet that killed his wife and child, so it's either a Russian guard or Wilk. Though Tsurumi seems to think that it's Wilk.