The screams and alarms started going off just as Alix was finishing her poison distribution. She had not yet neutralized Afaro and his guards, which was a deliberate move on her part. The captain needed to work out some of his aggression while she wanted to test out the strength of the guards and Afaro personally.
Because of the noise, it became noticeable that a lot of people in the stadium were no longer moving, they were as stiff as corpses with the exception of their eyes which were roaming around in fear.
The previously loud stadium was now filled with an eerie silence as they became alerted to a looming danger. Those that had not been paralyzed by the poison resorted to screaming and running which made them easy targets for the soldiers who shot them with bullets that paralyzed them as well.
At least Alix's poison was painless, the one coated on the bullets was more deadly, and the infected parties were howling in pain.