I had a more emotional ramble about it here, but I’m going to go on and speculate some on it’s possible meaning and reasoning now.
Mona’s murder was extremely violent. Judging by the state of her house, this person wanted her to suffer and wanted her dead. It was an up close and personal killing that had involved a struggle and Mona to be attacked again and again.
It was full of rage.
This person didn’t simply want to shut her up, they wanted to punish her. They felt personally attacked or endangered by her. Mona’s shocked expression when she saw whoever it was standing in her room shows that (again) this was personal. Her reaction made it seem as though she knew this person and was both surprised and afraid. It’s even possible that they were wearing an Ali mask which could cause the same reaction from Mona.
Her reaction is what makes it more apparent to me that it wasn’t Alison like the show is trying to make it look like. She wouldn’t have been so surprised if it was Alison. It’s obvious that two different people were in Mona’s house before she was murdered, though it’s hard to say if they were both in there at the same time. The way it’s shot makes it seem like one person, but the hair shows that it’s clearly not, so it’s possible that there is a gap in time in which the “Black Hoodies” are in the house separately.
The “Black Hoodie” on the stairs could have been Alison or someone with a similar build and hair, but that girl is not the one who entered Mona’s room. It’s possible that person didn’t intended to harm Mona and maybe was after the information she had instead. It’s still possible they did want to hurt her or was with the other person, but it’s not clear, so it’s open for guessing.
The one with the choppy hair cut is the one who wanted to make Mona suffer. This person is clearly psychotic. As I said, the amount of violence in this murder shows that it was personal. This person hated Mona. Mona had to have done something to them to make them feel victimized and this is how they sought revenge. There are a lot of extremes revolving around issues with power and control in this show. Mona’s murder is clearly one of them.
She did an awful lot as -A and it’s possible that the Liars aren’t the only ones she harassed that way. She stepped on a lot of people when she clawed her way up the social ladder as well. She spent some time at Radley and may have even met this person there. Whatever she did to this person, it made them want to tear her apart. I personally think it was very likely caused by a betrayal.
Going off the possibility of a betrayal, -A had been gunning for Mona for quite some time. She was no longer useful to them. Her attacks were petty and no where near the brutal level this -A is on.
"Mona played with dolls, I play with body parts."
This is why I find it highly likely that it was -A that killed her. Mona was getting closer to figuring out what may have happened “that night” and was finding connections. She was doing this with the Liars. -A was done with her, but with her jumping ship it could have felt like a betrayal. She was helping the girls and she wasn’t supposed to help them. She was supposed to be against them.
This -A is clearly deeply tied to what happened “that night”. They had even told Alison that they watched her mother bury her. They more than likely know the truth about what really happened and was part of it. There are still some unexplained deaths and it’s highly likely that this -A killed them.
Those deaths were pretty clean though. It wasn’t as sadistic as Mona’s. Either -A wasn’t directly involved in her death, or they were pissed with her. I just feel like -A is involved in some way though. -A is a group, and it’s possible that it wasn’t a group decision to kill Mona this way.
It could be one of the group members going rogue or it could be that Big -A is truly that twisted. Going back to, “I play with body parts.” -A has played with and staged both Ian and Wilden’s bodies. They killed Jessica to mirror Bethany and to get at Alison.
-A has sent human bones to the girls in the past. Teeth, fingers, just where did -A get those? Are they from some random person/people they dug up in a grave yard like when they dug up “Alison’s” grave? Was it really even Bethany in there to begin with? Are they the remains of others they’ve killed? What do they plan to do with Mona’s body now?
They took her body, so they must have a plan for it. They may stage it to make a statement like with Ian and Wilden. They may make it a more personal blow with where they place her like with Jessica. They may send the Liars pieces of her like the other parts they’ve received in the past. They’ll more than likely try to make someone else look guilty of it too. What ever they plan to do, it will be awful.
Just as Mona’s death was intended to hurt, what they plan to do with her body will be intended to hurt the Liars and/or Alison. With Alison already looking fairly guilty of Mona’s murder in the fandom’s eyes and her looking fairly guilty of being -A in the Liars’ eyes, I’m positive all of it will be pinned on her, which should make it more apparent to the fandom that Alison is not responsible.
This show has been signed on for a seventh season. It wouldn’t be solved just yet. It’s illogical to believe that Alison is behind it all after we’ve seen so many moments of her own pain and fear at hands of -A. If that alone isn’t enough, remember the writers have to milk this for seven seasons. They wouldn’t just have two seasons of knowing who -A is as that kind of defeats the whole plot of the show.
I’m uncertain of the meaning behind replacing Jesus with “Loser Mona”, but it was clearly done for a reason. It’s meant to symbolize something, but it’s hard to say. The most likely is that Jesus had died for our sins, insinuating that Mona had died for the Liars’ sins. He was killed slowly and painfully, like Mona appeared to have been. Jesus suffered for us, as Mona had suffered for the Liars.
I’m getting more rambly than usual, so I think I’ll stop here. To sum it up - Mona’s murderer is certifiably crazy, the way she was killed showed a lot of rage, they plan to play with her body, and more than likely will make it look like Alison or the Liars are responsible. They had been texted, "It’s all your fault. -A"
The second to last paragraph…so sad.