You need to pick the right text that is linked to the Police that collides with the bullet. You can do this by putting them in a container so that when you pick the police it will pick automatically the text object.
Alternatively, you can pick the text differently if you dont want to use containers, how did you pin the txt to the policemen? If you use Hierarchy then you can just do:
PolicemanPick child Txt object
You do this after the collision in a subevent
Update:
Also, you have many issues with your code not related to the txt issue:
1-On collision is the same as overlapping but triggers once so you dont need to check for extra overlap on your second condition you can remove that.
2-On collision already picks the policeman so you dont need to save the UID and picked again as it will maintain the picking throughout that scope including subevents, so you can remove that too.
3-Trigger once you dont need it swell as the "On Collision" is already a trigger once, any actions you have there it will run just once.
Here is how it should look:
On Collision:----------- substack 1 from health & destroy bullet
----Sub: Hierarchy Pick child txt: ----set txt to policeman health
----Sub: Policeman Helath <= 0 ------ Your Actions