If your boss hasn't left yet, talk to them. Ask if there's a runbook and what credentials you'll need. Both aren't just reasonable questions, they're required to be known to complete the task.

If boss is gone, go to their supervisor.

Do this today. Assuming you're in the US, you have most of the workday to figure out what you know and what you don't.

And, as somebody else posted, calm down. Either your boss trusts you, or your boss is an arsehole. Either way, that's a good thing to know now. In the first case, great. In the second, no great, but you know you don't want to work for him beyond this internship.