As an engineer developing a product that can behave in a potentially fatal way it would be your responsibility to become aware of the failure modes. If this were the circumstance I would advise asking your boss for a "Lessons learned" or auditors recommendations arising from the incident.
As an intern this becomes a bit of a grey area since your level of individual responsibility should be low enough that you are not able to introduce failures. As an intern I would be more cautious about asking your boss for these things. Unless your boss is extremely accessible I would instead reach out to a co-worker. Whoever you reach out to, remember you are looking for clarification and not gossip. If the person you ask seems uncomfortable at all, drop the subject.
Late edit: I just realized that there is a reasonable path to this information without much risk of offending people who can affect your career. Ask your Health and Safety department about the nature of the accident and the lessons learned. Of anyone in the organization they are going to be ones with a responsibility to demonstrate safety culture. With them there is much lower risk of being seen as a vulture by asking about this as you feeling confident that you are safe on the job site is a part of their job (or at least it is in my organization).