Urgent need of advice: Should I leave him for this? My sister was injured bad.

I could go on and write about this for pages and ages but this isn't my diary so I'll just get to the point. This all happened yesterday.

My little sister, Abby, was staying with me and my boyfriend of 3 years in our apartment. We were all up pretty early and the food was pretty low so I told him (we'll call him Nick) I was going to get some food. He was on the phone. I wasn't really paying attention but I think it was his brother on the other line. Abby was rolling on the floor with our dog Tolby, watching TV. He nodded and I got my stuff and headed out. I went and did what I said I was gonna do. I stopped to talk to one person for a while but that was really it.
I come back and Nick is acting really jumpy and guilty. He told me Abby was sleeping but he kept trying to distract me from checking on her by volunteering to do it himself. Luckily he's a bad liar and I knew something was up. He was shaking and his head wasn't all there. Every possible ****up ran through my head while I tried to figure out why he was acting weird but like an hour later he finally admits something happened to Abby. I go in the back and she's in the bed. She looks like she's sleeping but when I move her there's blood on the pillow. My ****ing head goes off and I ask him what the **** happened. According to him he just wasn't paying attention. He let her out on the patio--we live on the 4th floor--and didn't know she was playing on the railing (even though he knows she likes to try to sit and play on them). He said maybe she was sitting or trying to walk along the rail and fell off.
We took her to the hospital in his truck. We told them it was an accident and that she fell from the 4th floor of a building and relevant info, whatever they asked.
I couldn't stay there. I know I wasn't even there but I feel like this is partially my fault and terrible that I can't stay. I know it was an accident but I'm pissed with him. I don't know what's going to happen to Abby or to us. If she's seriously hurt which I think she is will they charge us with anything? And I'm really just trying to hope for the best for her because it's all I can do. I don't know any medical details. I just hid in the bathroom, they talked mainly to Nick. But I know they'll have to operate because her skull was damaged. Cracked or fractured or something. Now how am I going to tell my mom what happened? She let Abby stay with us for a few weeks while she rehabilitates her leg from a prior injury. I don't know if the hospital has already contacted her but inside I'm hoping they have so I won't have to explain when Nick and I call her.
But yeah, I'm pissed at Nick right now. I want to maul him. But I know it was an accident. It could just be my anger talking.This has made me seriously question whether or not I want to have a baby with him anymore. What kind of parents would we be? I just want to know if you were in this situation--would you stay and work this out or would you leave your boyfriend of 3 years and friend for longer? If she dies or has bad brain damage or anything serious I don't know that I could look at him anymore or myself in the mirror or my mother in the eye.

By the way Abby is only 6 years old.

Sorry to hear it and I hope your little sister makes a full recovery.

I think right now you need to focus on the issue at hand with your little sister. Be there for her and your family. That is the number one priority. So take care of that first and give yourself some time to think.

That seems VERY irresponsible for an adult male to let out a 6 year old child who he KNOWS like to play on the railing. It's almost like he was letting the "dog out" or something. That was completely his fault and he is 100% responsible. If I was your parents, your boyfriend would be in the hospital along with your sister.

You need to get rid of him. Immature negligence like that is a BAD sign.

I'm sorry, you're worrying about your relationship when your sister could be dying? Are you ****ING serious? I mean, are you ****ing serious?

And yes, most likely your boyfriend and you will be charged with a crime; she ****ing fell four stories and your boyfriend tried to hide it? And it took you an HOUR after you got home to go check on her?

And you're worrying about YOUR RELATIONSHIP!?!?! Usually I don't make personal attacks on forums, but you sound like a terrible person. Your sister could be dying and you're worrying about your relationship and YOUR GUILT?! ARE YOU ****ING KIDDING ME?! WORRY ABOUT YOUR GODDAMN ****ING SISTER THAT YOU ARE EXTREMELY RESPONSIBLE FOR HER CONDITION. YOU LEFT HER WITH, APPARENTLY, A COMPLETE IDIOT WHO THEN TRIED TO HIDE HER POTENTIALLY FATAL INJURY. WORRY ABOUT YOUR SISTER.

I hope she gets well.

I completely agree with damn2010, though if it was just the accident, I would go for forgiveness. But the way you are telling the story, he tried to weasel out of his responsibility at the expense of her health. What a douchebag (what an understatement).

When I asked him why he didn't take her to the hospital ASAP he said he thought she was dead. I thought she was dead too but I didn't want to take any chances. Her pulse was very faint. Neither of us felt it. I guess that's why he tried to cover it up. And it pisses me off. It's not like I was never going to find out. And I am worried about my sister, trust me. But she's being taken care of and I can't do anything for her right now. All I can do is tell my mother and hope they're both alright and be here for both of them. Nick's stupidass did suggest that we go somewhere 'until this blows over' like Canada or somewhere because he knows there will be consequences and he's scared but I shouted that down pretty firmly--I am *NOT* leaving my family. He's apologized about a million times and I think he's genuinely sorry. He looked like he was about to cry at the hospital. He does love Abby. -BUT THAT DOES NOT EXCUSE this situation. Nothing will.

I seriously hope you are just trolling.

In the unlikely event you aren't, of course you will have to get rid of him. How could you ever look him in the eye again, knowing what he did, whether by accident or not?

And yes, this sounds like it would be a devastating injury.

He'll be in jail soon, so you don't have to worry about whether or not to stay with him. Problem solved!

Why would he intentionally harm the child, what would he gain from that? I can't believe you'd even consider that the case. How do you think your BF must feel right now? He has your sister to worry about, the police, and now you. I feel bad for your sister, but the way you are acting is completely selfish... your sister and your BF are in a much worse position than you are. If the idea of you not being able to look at yourself in the mirror is your main concern then you have more problems than you think you do.

Yes, he was at fault BUT so were you. You should have waited until he had stopped his phone call and then explained the situation to him. Neither of you should be allowed to 'look after' children.