Right, as an older brother and as a father, I can appreciate your concern for your brother and for wanting to see him make good choices.
However, I think you need to walk back from the reflex to seek "punishment" for to behaviour that you do not think is good for him. There are two key objectives to keep in view - communication, and boundaries.
It's great that you already have a positive, communicative relationship with your brother. That's a great start. You're both in the age range and stage where we men tend to be terrible at communication, and we don't tend to look far outside of ourselves, and so it might take a lot of work to keep fostering that type of communication over the years ahead.
You said that as he tried to explain himself, you were too angry to deal with it - it's great that you can recognise that. When you notice that about yourself or him, that's the time to take a break, calm down, and then reattempt the conversation. Listen to him, relate to him, understand where he's coming from. Get his buy-in that you understand what he's done - if you can get there - and the rest of the conversation is much easier.
Set Clear Boundaries
Whilst I appreciate the view that your brother is nearly a legal adult, if he's 16 and already in your care, then I would venture to suggest that his (your?) parents were not able (for better or worse) to provide him the types of structured boundaries that kids need to thrive and feel safe. In many ways you're probably both dealing with that reality too, and so that will be weighing on any situation.
So, though it's not your fault that he is where he is, you're in charge of boundaries. Boundaries are positive things - they're safety fences to help us build a strong and safe life, the ideological opposite to punishments, which are there to make us feel bad. You've not had the full 16 years of parenting experience in setting those boundaries, so it's totally understandable that it'll take some practice to catch up.
Think through a short list of realistic and fair boundaries for him, for example:
- Under what circumstances do you expect him to contact you?
- What time should he go to sleep by and be up by, on weekdays and weekends?
- In what ways does he need to share in or contribute to the upkeep of the house?
These should be positive things that have a clear reason and are for his good. Stepping over them should have simple, fair consequences that are known in advance. Perhaps the WiFi gets switched off, or he has to do extra chores. Perhaps he's unable to go out for a set number of days.
So you want to have a frank and positive conversation, understand where he's coming from and how he's feeling. Once you've reestablished positive regard and respect for each other, explain what your hopes for his life are, explain the boundaries you think would help him in this age and stage, and explain what the consequences will be for crossing them.
Perhaps for this occasion give him an 'easy' token consequence, or waive the consequence as a gesture of goodwill. Set things off on the best foot for the next occasion. Especially given that his 'fault' was a kind thing he wanted to do for somebody he cares about - that's something to affirm and encourage, because that will make a good man out of him!
All in all the job you're trying to do is care for him emotionally and physically, as well as set him up for success in future. You want to teach him how to care for himself and set good boundaries for himself before he's responsible for doing that.
All in all, you love him and want the best for him. And that's got to be the key message that sets the context for whatever you need to do to help him live his best life.