My sister's boyfriend punched me over a huge mistake that wasn't my fault and hospitalised my sister. Where do we go from here?

I (21f) have a sister (Callie-26f) who is allergic to gluten and strawberries. She has been dating Mark (28m) for a year now.

Gluten makes Callie bloat, her stomach goes funny and she feels 'gross' (her own words) but her strawberry allergy makes her break out and depending on the quantity, her throat swell. She has an epi pen.

For Callie's birthday, I decided to get a cake made. I went to a bakery that specialised in allergies and dietary restrictions. I made it crystal clear about Callie's allergies/intolerances and they said it was no problem. I got her a gluten free chocolate and passionfruit cake (one of her favourite food combinations).

Well, fast forward and we eat the cake and 20 minutes later, Callie looks very red. Her eyes are swelling and she says she needs her epi pen. Mark takes her to the hospital and they're gone in minutes.

I'm freaking out because how could this have happened? I call the bakery and the women on the phone confirms there's no strawberries or gluten in the cake. She also got her manager on the phone to give me a full refund (it was an expensive cake- for me at least).

I'm also texting Mark and Callie to try to figure out what's going on and to make sure Callie is ok. Callie didn't open my messages (understandable) but Mark left me on read. Even when I was begging for updates.

He arrived at mine 2 hours later to pick up their things because they left in such a hurry. He wouldn't even talk to me, or look at me. I'm sobbing because I would never hurt my sister and no one was telling me anything.

I'll admit, I yelled. I told Mark he isn't going to leave without giving me an update. I didn't get in his face, or personal space, but I was yelling pretty loud. The next part is a blur. I just remember a dull pain and hitting the wall.

Mark had punched me square in the face. He started yelling back about how Callie isn't responding because she's in the hospital 'because of your [my] actions' and that he's beyond pissed at me for not being more careful about cross contamination. I'm sobbing even more but before I could even say anything, Mark was already leaving, and I wasn't going to do anything to make him stay.

I have a black eye from the punch. I asked my mum what to do and she suggested reporting it but when I tried, I was told there was no evidence Mark did anything so a report couldn't be made.

My family know what happened, including Callie, but she doesn't seem to care.. she just keeps saying Mark is protective over her and was furious at me for my 'mistake'.

She doesn't seem like she's breaking up with his any time soon and while the family doesn't like Mark now, they're all reluctant to ban them from family gatherings.

What the hell do I do now?

EDIT: to those calling this fake because the cops were dismissive of my case (which... wow what a shocker. 40% and all) I don't know what to say. They literally laughed at me and told me I couldn't report. That's what happened. I don't know what to say. It's almost like bad cops are bad cops.