Corrected entry: Why did the two aliens gang up and kill the third one to escape the holding cell? Later in the movie, it is established that these mutated aliens can apparently regurgitate their own acid blood as a weapon, so slaughtering the other alien wasn't really necessary; they all could've just vomited some acid on the glass or the floor and gotten free without dwindling their numbers.
Grigory the Wanderer
6th Jan 2004
Correction: It took a lot of acid blood to burn a hole in the floor, and vomitting produces little amounts - just enough to hurt an enemy. It's not really a mistake - the aliens did it the faster and more reliable way.
Grigory the Wanderer