Shooting at Somebody With an Airsoft Gun

My question involves criminal law for the state of: Maryland
So I'm 16 and never had legal trouble before, this event is probably the only (even remotely) violent thing I've ever done.
This large 8th grade kid has been bullying my small 6th grade little brother at school and on the bus stop. However I never said anything to the school or parents because I was paranoid about it turning into one of those cases you always hear about where the school doesn't do anything or the parents don't believe it.
So one day at home I just decided "I'm gonna scare him away today".
My little brother's bus stop is two houses down from where we live. I heard the bus pull up and got my airsoft rifle ready and when the kid was a little ways past my house I fired a burst at him that lasted a little less than 2 seconds.
He immediately ran home and told his mother.
(Note: he didn't bully my brother that particular day, but I decided today would be as good a day as any to scare him off)
The cops thought that he had been shot at with a real firearm until they say that he has tiny marks from bbs. They came to my house and I complied with everything they said and we had a calm conversation.
The officer said that I was going to court for second degree assault.
Before the officer took his leave I asked if I should go down and apologize to the family, so he took me down to their house where I apologized to the mother and her son. She was extremely calm and much nicer than she needed to be, and she even made her son apologize for the bullying (he admitted to it).
They don't seem like they're gonna press charges, but the officer said that even if they don't, the DFPS probably still will.
I don't know if it's worth noting but when I fired at the kid with the airsoft gun I was only intending to scare him from trying to do anything to my brother, I didn't intend for the bbs to cause any harm. The airsoft rifle was over 3 years old and they degrade a lot over time, do I didn't expect the rifle to still have enough power to cause any pain.
How likely is it that I will be charged with the second degree assault?

You need a lawyer and can likely get the charges dropped in exchange for community service.

Charges dropped? Well not directly. You might go to court and get an agreement for a stet which means if you can possibly stay out of trouble you won't end up with a criminal record.

Putting fear of harm into someone is the definition of assault. The fact that you didn't actually have the ability to harm them is immaterial.
Get a lawyer.

The worst thing is, you decided to do something this dangerous and illegal, but you said you were scared that telling his parents would go nowhere. You didn't tell the school, nor did you tell your own parents. The reality is, this was extremely stupid and dangerous! Not to mention that you did not pull the gun out to scare him, you actually used it! You shot the kid not knowing what kind of actual damage you could have really caused. At this point, you could easily(and shouold be) charged with aggravated use of a weapon. This kid didn't realize what he was hit with until he actually made it away from the threat! Your parents need to get you an attorney. This was absolutely reckless!

I am assuming this was an AEG battery powered airsoft rifle? They do not get weaker with age unless there is a major design flaw (over compressed springs)

You could have easily destroyed his eye or tooth, or done the same to anyone else in the area. Airsoft requires safety gear for a reason.

If you are charged hire an attorney.

It matters not if the thing shot marshmallows or not. If the intent was to "put fear" in someone and the person reasonably believed he was about to be harmed, that's all the elements need for assault.