Reaction fire during your turn

[Caaygun]

So how to survive this situation when sebillians is at the front of your dropship?

Using flashbang will hopefully suppress the alien, then you can kill him, he is immune to smoke.

I use a layout where there is 1 machinegun and 2 shields or heavily armored soldiers in the front. Never had any big issues with aliens in front of me. Usualy I'm just happy if some mook decides to check out the Chinook and proceeds to sit in the firing lane of a machine gun. I guess maybe if an Andron spawned in front of a team with nothing but ballistics. I also always have some (hopefully armored) people exit from the sides because I once got shot in the back by a Sebilian who had spawned near one of the side exits.

Now, I use shields in front too, somehow it feels like they might block the guys behind, but actually they don't. Now I often crouch everyone, then shoot him with a sniper, or escape from sides depending on the enemy angle.