You hear footsteps shuffle in the hallway outside, slowly heading towards the door to the lab. Oh no, someone's approaching! One of the military, judging from the sound of boots on the linoleum tiles. How would you tell them that you're not a threat before you got riddled with bullets if you can't speak human words with this reptilian maw? Then you smell it. The smell of lizard juice is on them -- they've been infected too. It's fresh, though you don't see, hear, or smell any living lizardpeople in the vicinity other than yourself. Your heart sinks at the thought of losing another one to the bestial masses that your project inadvertently created.
Your reptilian phalluses, on the other hand, stiffen up and begin to throb, the tips beginning to leak -- even though you've retained your human mind and higher faculties, it seems like the transformed lizardpeople have a significantly higher subconscious urge to mate (after all, even with the serum you still left quite a mess in the lab), with your own conscious desire not to worsen the reptilian apocalypse being what's stopping you from becoming a mindless horny lizardman. It's still rather bewildering for you, as a few minutes ago you didn't even have one of these things protruding out of your groin and now you had to resist the urge to grab two of them at once with your hands -- mindless you are not, but horny still seemed to be the case. It'd be embarrassing if the situation wasn't so serious.
The doomed soldier, meanwhile, makes it to the door of the lab you're in. You do notice first the fact that they were holding a pistol that they immediately tried to use on you when spotted only for it to click empty (thankfully), but then your eyes widen in shock and you let out a reptilian growl as you realize the soldier is...