Ridiculously quick fermentation?

I'm brewing my first batch of beer, and I had a couple questions!

So, it's a red ale, and it's from an extract kit. Jug of LME, some specialty steeping grains, couple oz of hops, and some dried yeast. Nothing too special/crafty!

I finished brewing it Friday night, and am fermenting it in my 5 gallon glass carboy.

I come back the next morning, and my beer has taken fire - tons of fermentation occurring, big krausen on top.

A day later - maybe later, actually; probably closer to 18 hours, the krausen is starting to subside. The airlock has completely stopped bubbling, and now about... 3 full days after I set it to ferment, the krausen is nearly gone.

By contrast, my friend's brew (we brewed in tandem on Friday) is happily fermenting away, with a huge, solid krausen, and has been steadily doing that for about 2 and a half days now.

So yesterday, being the concerned brewer I am, I took the gravity of my beer, and I believe (this was a rather wonky gravity reading, as I had an imperfect container to measure the gravity in), my brew was sitting at about 1.014-1.016, which after 3 days seems to be a decently low gravity.

My concern is that it's gonna stay there, or that my reading was poorly done, and my yeast are completely shot. I've never heard of a fermentation occurring so rapidly.

Is this because of my 5 gallon carboy? Not enough aeration beforehand? Or maybe I'm just being completely neurotic about the entire process, and my beer is fine!

Either way, def. would be curious for some opinions.

If you pitched above 70 it may do that. You may not get a complete finished gravity after 3 days because they still slowly ferment.Its pretty early. My concern would be why would you want to check so early?
Did you use the same yeast as your friends same pitching temps? same beer to drink whilst making the beer. Were the ambient temps exactly the same as your friends?

I was floating on the 70 mark, probably.

We brewed two different styles, so I know his is obviously gonna act different than mine, but watching his beer fermenting for 3+ days started worrying me.

The ambient temps are both exactly the same.

Only reason I checked is because of the lack of krausen, and the quick fermentation. Once I checked the gravity, I felt stupid, because now I have to worry about whether or not I contaminated my brew.

Still, I'd never heard of such a quick fermentation into a lull like that, so I freaked out.

Half my brews went that quick and if you used dry yeast its fairly common.Although for some reason i feel im going to have a better brew if it is slow and consistanly longer too. I know what your sayin. Was his stlye a higher alcohol beer. It all depends really the yeast will do what they want to do. try pitching on the lower end this is where im at i was pitching 70 + and getting esters that take along time to condition out.
Since it was so quick i would maybe let it sit at least 3 weeks before botteling.
YOUR gravity also depends on you steep temps if you were above 155 youll get more unfermentables at below 153 more fermentables . So maybe you steeped higher causing a higher finish gravity , but it is still too early for a final gravity probably. I always rouse my yeast alitlle by twisting the carboy carefully and raising the temp after the 2nd week. Hope this helps a little.

Thanks for the words, definitely helped out a lot!

three days is a completely reasonable time to be done in in my opinion.. or least to appear to be done. May lose a couple more points over the next week, I wouldn't rush it, but no reason to worry or do anything either. depending on beer style and OG it may be done, might lose a few points. Just make sure you wait until it reaches a steady FG before bottling (same gravity a few days in a row). Would probably be better to let it sit on the yeast for a week or two in any case - make for a cleaner tasting and clearer beer. cheers!