What if we put in a twist and take it away from the gun toting special agent? Make multiple playable characters.
You are a normal guy/girl. wake up, world is normal, do a job for your father, go to shop for mum.hear news about a deadly virus etc, come home to see parents turned into zombies, you dont know where to go.
See attacks breaking out all over, traffic jams, hoards of dead bodies and zombies. You have to find a safe haven - typical zombie stuff.
Then switch to the stars operative. You go into this place, and you can rescue people, NPCs who are not related to the plot but have a little scripting. These people can be given jobs, need motivating, directing etc. They can die. They might be bitten but not tell anyone. You can kill them yourself.
Eventually your two characters have to meet up and you have to save the city.

Even if it aint Resident Evil, this game needs to be made ffs.