Here is how Malfunction explains and Human Fluttershy's explanation goes in Code Red's Adventures of My Little Pony Equestria Girls.
(After a break, we see Malfunction telling everyone about Flash Fire)
Major Malfunction: I met him when he was a thief on the streets. I took him in and taught him at my school.
Sunset Shimmer: What happened?
Major Malfunction: Like you Sunset, he wanted more. He aced all of his classes, combat most of all. But it wasn't enough for him. I tried to tell him what we want and what we need are two different things, but only drove him away. Seeing where it was going, I knew I would have no choice but to expel him. If only I had known then.
Sunset Shimmer: Why didn't you tell us anything about this before?
Major Malfunction: Because I buried the past and forgot all about him. I get nightmares about what happened.
Light Ultron: He got wind of it, didn't he?
Major Malfunction:(nods) When he found out, he was furious. In retaliation, he drove his melee weapon into the chest of one of his fellow students. They all fled. One of our janitors ran at him to avenge the student, but Flash Fire shot him multiple times.
Nighlock: What did you do boss?
Major Malfunction: I confronted him.
(we see Flash Fire(in Cybertronian form) on a cliff)
Major Malfuntion:(in flashback) It didn't have to be this Flash Fire.
Flash Fire:(in flashback) You're soft as you are weak.
Major Malfunction:(in flashback) You are making a mistake.
Flash Fire:(in flashback) Or am I?
Major Malfunction:(in flashback) You turned all of us against you.(unsheathes his swords and activates his Triple Bladed Sword and Cosmic sword) And now, I will do what I must.
Flash Fire:(in flashback)(takes out his own swords)
(Battle of the Heroes plays)
Major Malfunction: We fought for a long time before he made his escape. And that was the last time I saw him.
(we see them duel until Flash Fire escaped)
Major Malfunction: I trained him to do good. But he used that training to do evil.(to Human Fluttershy) So are you alright?
Human Fluttershy: Yes I'm fine.
Bucky Barnes: What's your name kid?
Human Fluttershy:(quietly) I'm... Fluttershy.
Twilight Sparkle: Sorry what was that?
Human Fluttershy:(quietly) It's Fluttershy.
Twilight Sparkle: It sounds like you're saying Fluttershy.
Nighlock: That's because she is.
Twilight Sparkle: How do you know?
Nighlock:(taps his right ear) Enhanced hearing.
Twilight Sparkle: Oh, o-kay.
(Human Fluttershy looks over and sees Spike)
Human Fluttershy: Oh my goodness! Who's this sweet little guy?
Twilight Sparkle: That's Spike. He's my...dog.
Human Fluttershy: Oh, he's so cute! Go on, eat up little pup.
(She gives him a dog biscuit)
Human Fluttershy: oh, wouldn't ya just give anything to know what they're really thinking?
Twilight Sparkle: He usually just tells me.
Air Strike:(shakes his head and motions for her to stop talking)
Human Fluttershy: Oh, w-what do you mean?
Twilight Sparkle: Oh, uh, nothing.(chuckles)
Sauron:(under his breath) Yeah nothing.
Nighlock:(glares at him)
Sauron:(makes the "What the flip" motion)
Twilight Sparkle: Flash Fire said you picked something up. Something that belonged to him. It wasn't a crown was it?
Human Fluttershy: How did you know?
Major Malfunction: Maybe she's like Charles and Ms. Grey. Maybe she's a telepath.
Sunset Shimmer: You do realize that everything with abilities isn't always a mutant right?
Major Malfunction:(smiles sheepishly)
Twilight Sparkle: Uh, lucky guess. Do you still have it?
Human Fluttershy: Mm-mmm.
Firestar: But you know what happened to it?
Human Fluttershy: Mm-hmm.
(Some of Code Red's agents get out note pads and put on glasses and a moustache)
Human Fluttershy: This morning, I was passing out flyers for the animal shelter like I do every Wednesday.
(we see Human Fluttershy by the pedestal)
Human Fluttershy:(in flashback) Canterlot's animal shelter needs more volunteers. Won't you help an animal who can't help itself.
(no one does)
Human Fluttershy:(in flashback)(whimpers)
(something then hits her on the head)
Human Fluttershy:(in flashback) Ow.(sees the crown and picks it up)
Human Fluttershy: I have no idea how it got there. But I didn't want anything to happen to it, so I decided to give it to Principal Celestia.
Twilight Sparkle: Principal Celestia?! She's the ruler here?
Human Fluttershy: You could say that. Technically, since she and vice principal Luna make all the rules.
Nighlock:(in a terrible German Accent) I completely concur. Betamon, what is your conclusion?
Betamon:(in a German accent) Zhe zame.
Nighlock:(in German accent) Mushroomon?
Mushroomon:(in a German accent) Zame.
Nighlock:(in German accent) BlackAgumon?
BlackAgumon:(in a German accent) Zame here.
Nighlock:(in German accent) Okay. DemiDevimon, what is your conclusion?
DemiDevimon:(shows them a picture of when Human Fluttershy would turn her eyes to look at Quicksilver and blush)
All of them:(laughs)
Sunset Shimmer: Thank you, Fluttershy.
Human Fluttershy: You're welcome, Sunset.(bell rings) Oh no, I'm late for class.(leaves)