Police have now arrested one teen who was allegedly involved in placing pieces of metal onto the subway tracks in recent months, causing mini explosions. Brooklyn resident Keyshawn Brown, 16, was arrested Tuesday and charged with criminal mischief, arson and reckless endangerment for placing a metal railsign across the subway tracks at Nostrand Avenue last week. You can see a video of that incident, and subsequent explosion, below.

Police claim that Brown placed the railsign on the tracks last Thursday morning. The explosion was caused when an incoming C train struck the sign. They say that Brown created "a risk of train derailment, risk of injury or death to passengers who were on that train, and caused over $5000 of damage to MTA property." In this particular incident, the motorman hit the emergency brakes, and no one was injured. Cops adds that Brown is being charged as an adult.

As we reported over the weekend, this was just the latest in a series of similar train incidents that allegedly involved Brown. A subway motorman, who asked to remain anonymous, told us Brown and his friends caused extensive damage to seven trains stored in Queens a few months ago: "They pull emergency brakes on trains and run off. They have keys to the operators cabs. NYPD doesn't seem to want to do anything."

He offered more information about the group of teens, whom the Post says call themselves "Conquestors."

It's well known amongst the "buff" community that they are the culprits...They commit the crimes and then brag about it on the Internet (mostly Facebook) until someone says something and it is taken down...They have been messing around stealing rollsigns for a few months now. [They messed with the] 7 E F and R trains around Parsons Blvd. They have to be stopped. I've spoken to the police myself, and was told they have to be caught in the act. They have train keys. They go in unoccupied cabs and make announcements. They activate emergency brakes and run off trains.

You can see two such examples of the Facebook bragging below.

CBS adds that Brown pleaded guilty last month to felony assault with a weapon: "The criminal complaint filed against him charged that he used a metal pipe to beat an associate over the head and telling him, 'That’s what you get for snitching.'"

The teen who was attacked reposted the most recent video, and wrote on Facebook that his assailant had been sent to Rikers but was let out: "They got locked up for almost fatally killing me in the back of my head with a break handle they already got locked up and THEY STILL HAVENT STOPPED...And they spent a couple days in Rikers and still won't stop."

Sally, the mother of the teen who was allegedly attacked by this group, has created a Facebook page called PAMTABullying to track their alleged crimes. She uploaded the graphic video of her son being hit over the head: "They hit him in the back of the head with a stolen motorman's brake handle - almost 3 lbs of steel (there were 6 kids in total, and they surrounded him). 3 of the kids were taking turns to video this."

If you can see this post - PLEASE COMMENT. Here is the video of what these "animals" did to my son (the short version) They hit him in the back of the head with a stolen motorman's brake handle - almost 3 lbs of steel (there were 6 kids in total, and they surrounded him). 3 of the kids were taking turns to video this. It also goes to show the "animals" we have to deal with everyday on the trains & buses. MTA NEEDS TO TRAIN THEIR PEOPLE BETTER - TO DEAL WITH THESE SITUATIONS! Posted by PAMTABullying on Monday, March 16, 2015

The mom tells us that her son was friends with the group for several years before this incident: "When my son decided he did not want to be their 'fall' guy anymore that is when the bullying started." She says she filed a complaint with the MTA last summer after the kids pinned the blame for their rollsign shenanigans on her son, and an MTA employee allegedly physically threw her son out of a station.

She says the brake handle assault happened on Feb. 15th:

This kid...called my son (who was in Dyker Heights for the weekend) and asked if he wanted to meet up. As my son was bored, he figured, he would go out for awhile. When he got to the Ft. Hamilton Station, they surrounded him, diverted his attention & hit him with a brake handle that they had stolen. My son did not tell anyone except his brother what happened, but his brother said if he got hit, how is he walking around & thought nothing of it. And the next morning these kids...had posted all about what they had done. They actually think my son snitched on them, when they actually did it to themselves.

She adds: "I did have to bring him to the hospital. The sad thing is that this kid Keyshawn slept over my house like 3 days before he did this to my son."

The teens involved in all of these incidents are also allegedly the same ones in the video below who were electrocuted while putting a sign on the tracks back in February.