Knott's Berry Farm in Anaheim, CA is known for it's Halloween theme and this year they added Special Ops: Infected
Participants will run around 6 acre lot lead by a leader and get to shoot prop guns with camera that will count how many zombies you got. When zombies get within 10 feet, you are "bitten" It's not just a run and gun and the event will have a plot.
According to the LA Times,
...enlistees will be tasked with completing a series of objectives with operation code names like Bulldoze, Derail and Tunnel Rat. Up to six squadrons will be in Camp Snoopy at any one time, hunting for zombies hiding inside buildings, under bridges and behind fences.
This seems to be a bit more intensive than Universal Studios: Japan's limited run Biohazard: The Real attraction.
From: LA Times