This is one of the images from the first teaser that we got. When I first saw it I thought Eggsy was shooting an enemy, but now the trailer this week shows who is the one in the other side:
And Eggsy doesn’t seem (in my eyes) relieved to see him:
Eggsy doesn’t have a gun in his hand in the first gif, so that could probably mean that the picture of the teaser takes place after that (and yes, I know that trailers are a mess with the timeline for movies). The question for me would be: Why is Eggsy pointing a gun towards who I suppose is Merlin?