I don't see any errors -- assuming that the police officer is male.
I suggest changing the sentence to:
When police officers fire their guns, they must fill out a lot of paperwork.
When a police officer fires his gun, he must fill out a lot of paperwork.
Correct pronoun errors? I don't see any.
2 answers
The structure of the sentence leads to an unclear image in terms of timing. I would add to Ms. Sue's version of the sentence.
When police officers fire their guns, later they must fill out a lot of paperwork.
Although I may be unique in my imagery, I had the image of "Bang, write, bang, write, etc." Adding "later" avoids this image.
When police officers fire their guns, later they must fill out a lot of paperwork.
Although I may be unique in my imagery, I had the image of "Bang, write, bang, write, etc." Adding "later" avoids this image.