You are a good neighbor. Your employee did the right thing because they did not know the contents of the pkg.
I am assuming the driver did the right thing by trying to get the pkg to the customer the same business day even though they were "out to lunch",
typical government but that is another thread..lol

( and I do it for $1.00 a year...really?? )
I am assuming the Chief picked up his
AR-15 police assault rifle when they got back from lunch/next am from your place of business. (sorry I just couldn't resist).

In firearm layman terms "AR".
Now come the questions.
Did the department receive the firearm intact? (I am assuming yes)
Was the firearm stolen or lost? (I am assuming no)
Did your employee or the driver have anything to personally gain during the indirect?
No.
Can a FFL or non FFL ship a firearm to a government LE agency?
Yes.
Did the shipper or PD suffer any type of loss?
No.
Now what I
KNOW about LE and ATFE if your Chief got his panties in a wad and dropped the dime the first two questions out of ATF would be the following.
1. Is the firearm stolen?
2. Is the firearm accounted for?
"thank you for calling us and we are glad you got your AR".
It is what it is.
Now if you want to continue reading I will relate two stories that I have personal knowledge of and every word is the
fact.
I have been a "hobby" FFL since 1986, I worked out of my house as a second job. Before I opened the shop a delivery person left a package at my front door. No DSR, ISR just a residential delivery. I got home after
working all day and opened a Kreighoff over/under shotgun. It wasn't a big deal until I looked at the paperwork. The invoice was for $14k (more valuable at the time than a pre 86 machine gun) and it sat on my porch all day. Needless to say I called the delivery company and just asked for the driver to stop by the house. He did in about 20 minutes and I showed him the invoice and gave him a key to the house. Enough said about that.
Another dealer called me one time because he had shipped a MAC 10 (machine gun) and the label came off at a hub. He knew
who I worked for and was freaking out. It showed an inbound scan and that was it.
Nothing else.
I told him to request a trace and inform the agent the contents of the package and alert overgoods. Sure enough they called Frank the next day and had the package but no airbill. The package was returned to Frank. He "properly packaged" the contents and made sure the airbill was properly attached. He reshipped it and everyone had a good day. Now granted the pucker factor was up for 24 hours but FedEx got the job done. (I know my purple is showing).
That's all I have to say about that.