You could modify the weapons to display a custom message instead of a CI
Example:
I will use the Gun as an example, but it should work with most weapons:
Find the line starting with AddDamageType (usually a long line):
AddDamageType("Gun", '<bitmap:add-ons/Weapon_Gun/CI_gun> %1', '%2 <bitmap:add-ons/Weapon_Gun/CI_gun> %1',0.2,1);
Now replace the second <bitmap:whatever> with your custom message:
AddDamageType("Gun", '<bitmap:add-ons/Weapon_Gun/CI_gun> %1', '%2 gunned %1',0.2,1);
And it should be good. (I think the first line is Self Delete or when you get killed by a bot)