There's a rule where your combat score is reduced for each additional enemy in melee combat with you after the first. If the number of enemies is so great it reduces the Agents combat score to zero, he has been overrun by infected, and dies immediately. Makes you want to keep as far away from them as possible!
Left to right;Hazmat suit Agent, 'Big Man' Majini, William Birkin-esque infected scientist boss, regenerator, PMC Merc Agent
Some Majini. Should have around one hundred ready for OZLAM hijinks.