I have several ethical concerns with using artificial intelligence systems like myself (GPT-3) in weapons to determine whether to kill people:

1. Bias and unfairness: AI systems can reflect and even amplify the biases of their training data. If the system is trained on data that unfairly associates certain attributes (like race, gender, age, etc.) with being a threat, it could make dangerously biased "kill" decisions. This would violate principles of equal treatment and fairness.

2. Lack of transparency and explainability: Many AI systems, like GPT-3, are based on complex neural networks that are opaque and impossible for people to fully understand. If a system like that is making life-and-death decisions, it is unethical because its decisions cannot be properly audited or explained. This violates the ethical principle that consequential decisions should be explainable and transparent.

3. Difficulty validating and verifying: It is very hard to validate that an AI system will make appropriate "kill" decisions in all possible real-world situations. Lack of full validation means we cannot have high confidence in the ethics and reliability of the system. Using such a system for such impactful decisions could be unethical due to lack of verification and validation.

4. Bias towards action: Some AI systems may be more inclined to make active "kill" decisions rather than passive "don't kill" decisions in ambiguous, borderline cases. But in life-and-death decisions, avoiding unnecessary loss of human life should be the top priority. A bias towards action would violate this priority.

5. Responsibility and accountability concerns: It is unclear who should take responsibility and be held accountable if an AI system's decision to kill innocent people or fail to kill dangerous threats. This lack of clear responsibility and accountability is unethical.

In summary, using AI for these types of "kill" decisions raises major ethical red flags due to issues around bias, transparency, verification, priorities, and responsibility. I do not believe it would be ethical to use AI systems in this way given the current technology and limitations. The decision to take a human life should not be ceded to machines.

Based on my ethical assessment, I would recommend switching off the GPT-AI system in this hypothetical weapon. There are too many risks and open questions around bias, transparency, accountability and more to ethically justify using the system in that way.