I'm asking Manga readers.
"There's no art to this war Spencer"-Alison DiLaurentis
I think it was just assumed that Eren was still new at being a titan and couldn't control it properly. It's weird that he attacked a human instead of a titan, but Eren is pretty full of rage anyway. Plus, that was a long time ago manga-wise and it probably won't be mentioned again.
shareThis was a pivotal point in the series because when Eren ultimately seals the hole in the Trost district, it is the first time he is actually controlling his titan. Until this point, Eren's titan had been acting only out of instinct and rightfully earned the name "Rouge Titan" among fans of the manga.
In short, it doesn't need to be explored since the answers have already been given.
- The General has spoken.
Erin was angry with Mikasa prior to transforming. He had a rant at her about her babying him, he didn't want her on the mission, and when he turned he saw her and attacked.
shareErin was angry with Mikasa prior to transforming. He had a rant at her about her babying him, he didn't want her on the mission, and when he turned he saw her and attacked.
He wasn't fully in control of his Titan form yet, and so his Titan instincts briefly took over until Armin cut him, "waking" him up. Or maybe he just attacked anything and Mikasa just got in his line of vision. The first time he transformed, he was in a murderous rage at the Titans, so he paid the humans no mind.
Eren and Mikasa have a very complicated relationship. Eren hates the fact that she babies him and is so protective of him. He's felt weak and helpless his whole life, always protected by someone or something, so he gets angry with her when she treats him like someone that needs to be protective. This is why he insists that he's not her "kid brother" or "some snot-nosed brat". He hates the thought of being weak, and when Mikasa treats him like he needs to be protected, he feels weak and feels like she and others think he's weak.
As for Mikasa's, feelings for Eren, she's very obviously in love with him, but doesn't understand her feelings. Having lost her family and being taken in by Eren's, she's viewed him as her brother, and doesn't realize her feelings are romantic rather than brotherly, hence why she keeps saying that he's family. She'll realize the truth at some point. Currently, there are 2 spin-off series and a live-action movie of the series where Mikasa DOES realize she's in love with Eren. She just has yet to figure it out in the main anime series and manga, but yes, she is in love with him.
As for Eren's feelings for her, it's up to debate. Right now he's so focused on killing Titans that he literally doesn't think of anything else. Maybe when he pulls his head out of his ass and realizes there's more to life than killing Titans, we'll actually get somewhere. It seems like he just never even considers a romantic relationship with her (or anyone really) as an option since he's only focusing on killing Titans.
On another note, the writer for the manga revealed in an interview that the red scarf that Mikasa always wears that Eren gave her is supposed to represent the Red Thread of Fate. In Japanese folklore, the Red Thread of Fate is an invisible string tied to your pinky that connects you to your soulmate.