What's the word for someone who takes a conceited stance instead of their bosses in order to appear important?

Here in Brazil we call people like this "puxa-saco" (bag dragger?), meaning someone who invariably sides with and supports their bosses, often going against co-workers or employees in general, in an attempt to get recognition, be promoted, whatever. Often the boss doesn't trust them, but keeps them around as a self-maintained policing agent. Often they are quickly fired too.

Today I had an experience with a person like this. I went to see a person who happens to own a property around here and they were there, but sleeping. All I wanted to do was to ask for permission to enter the property and take close-up pictures from some beautiful trees inside the property.

I was received by an employee and he was extremely concerned about my presence there and my wanting to take photos therein. He talked and acted as if it was a mortal sin to ask that and even told me his boss would call the police if he saw anyone inside the property... Except that I was going there specifically to ask for permission.

I bet his boss wouldn't be half as worried as he was, at most he would deny me permission to enter the property, which is fine.

So that's what I wanted to know. Employees who act like that, what would you call them in English?

EDIT:

First, thanks for all the answers so far. I haven't decided yet which is better but all people who answered my question so far gave valuable answers.

It seems, however, that some people need more context on what I said, as they inferred stuff I did not write, or somehow understood me in a way I did not intend to be perceived.

DESCRIPTION

The property lay by the road, at the town's entrance. There are no walls, only a barbed wire fence around the pasture, and walking further, alongside the road, there's an alley that leads into the property.

Down that alley there are some stables and a house somewhere behind them.

The owner sells some goods he produces there, like milk and manure, a lad well known to the city folks.

There was no reason for the employee to be concerned. I met him as he was walking the alley up and out the property. As I see him I walk it down, but no further than he himself has walked up, then I stop, clearly signalling I wait him so we can talk.

As he gets near me he says nothing, so I say hi and politely ask him over his boss' whereabouts. He looked calm, on an okay mood until then, but immediately frowns upon me and tells me upfront that his boss was sleeping, as if it was personal to him that his boss not be disturbed. That struck me as odd though, it was 3 in the noon and the day was bright, who sleeps by then!?

Not impossible, but not customary either...

He proceeds to ask me why I want to see him, acting passive aggressively already, while I just don't get why.

I tell him why, he gets even more so... the most awkward!

Soon I'm talking to this pretentious mediator between a plebeian and some sort of king. If I could describe his stance with one word, it's unnecessary...

To make it all the more comic, the guy's wearing old work outfits, full of manure and dirt, the vision of an unimpressive rural worker. Totally okay, don't get me wrong, except that he acts as if he's the property manager and instead of a small farm, the whole matter is about a mansion or a castle...

At that moment I wished I had his boss walking up the alley instead, I sure would have had a better conversation...

EDIT 2:

I think the more info I add, the harder it's getting for readers to understand the context.

Bear in mind that when one experiences a situation, there are emotional and non-verbal cues that can't be transmitted in full via a written account. I was there and know the undertones of the situation. I felt offended by someone to whom I acted kind and respectful. I bet there's a ton of people around who'd just hop over the fence and take the photos right away.

Now, I said something about the lad's clothes and may have gotten misinterpreted. There's nothing wrong with working in farms and getting dirty. I myself work in the farms during the rainy seasons, and I get home just as dirty. That's a common job around here, the town has only 4 thousand inhabitants and most of us live off rural activities, my family included. My father, for instance, produces and sells vegetables.

The problem I was trying to portray is that I felt disgusted by the lad's attitude. Looking at him made me feel even more disgusted... "Who the hell does he think he is?" was my thought. I went there to ask for permission, exactly because I didn't want to be invasive, trespassing someone else's property. I know his boss is cool. During weekdays, people walk down that alley to buy cabbages, milk and such from him. The thing is, it was saturday, and I was going to take photos, so that might bother the owner, so let me not do that and ask what his thoughts are first, I thought.

Then as soon as that man learns what my purposes are, immediately frowns at me and gets pretentious, conceited, curt and unfriendly, talking in a kind of angry, agressive undertonte and purporting himself to be great mediator between a presumed idiot who wants to take photos from trees (because who does these silly things anyway?) and the most important personality in the town.

That's how it felt. It was uncomfortable, I felt offended and I didn't understand the need for him to act like that towards me.

As I got home I was still thinking about that weirdo. I was not resented, but thought to myself: "That was a great puxa-saco I met there". Immediately afterwards I thought it might be exciting to know what word might be like "puxa-saco" in English. So I turned the computer on and asked this question...

I hope I was clear this time around.

I discount the too-obvious sycophant because it does not necessarily have the overtones of being a servant.

Sycophant = someone who praises powerful or rich people in a way that is not sincere, usually in order to get some advantage from them

Cambridge dictionary

Minion is relevant but does not give the complete feel of your description.

minion = a person who is not important and who has to do what another person of higher rank orders them to do

Cambridge Dictionary

There are several other candidates. Your choice may depend on context. Here are three:

Lackey = a servant or someone who behaves like one by obeying someone else's orders or by doing unpleasant work for them

Cambridge Dictionary

Flunkey =
a person who does unimportant work or who has few or no important responsibilities and shows too much respect toward his or her employer

Cambridge Dictionary

Hanger-on = a person who tries to be friendly and spend time with rich or important people to get some advantage

Cambridge Dictionary

hanger-on is similar to sycophant. flunkey or lackey seem best to fit your example, with lackey implying a little of the ill-informed awkward aggression (the "unpleasant work" of the definition) that you describe.

Lower down the employment scale we might have goon, but they tend to be employed specifically for their aggressive role. The usage is stronger in America than on the eastern side of the Atlantic.

Goon = man hired to terrorize or eliminate opponents

Merriam Webster

In slang, we also find

Junkyard-dog = (idiomatic, by extension, hyphenated when used attributively) An animal or person with an especially nasty and combative demeanor.

Your dictionary

I like this one because it combines the elements of canine dependency on the master with the mindless aggression of defending territory. I have heard it used as yard-dog but find no source.

brown-nose (brown-noser) informal an extremely obsequious person.

obsequious obedient or attentive to an excessive or servile degree.

From your first paragraph he sounds like an a*se-licker, a crawler, a toady or a lickspittle.

From your next three paragraphs he is clearly a jobsworth. I have met him!

More on jobsworths at Wikipedia.