I'm sort of on the fence but I'm leaning toward turning them in, if I was ordered to do so by government. Why? Because God commands that we obey our government authorities. Edited to add that the reason that I say I'm on the fence is that I also recognize that, sometimes, good men need to use guns to stop guys like Hitler, Stalin, Mao, Pol Pot, etc.
Romans 13:1–2
English Standard Version
Let every person be subject to the governing authorities. For there is no authority except from God, and those that exist have been instituted by God. 2 Therefore whoever resists the authorities resists what God has appointed, and those who resist will incur judgment.
Romans 13:1–2

Let every person be subject to the governing authorities. For there is no authority except from God, and those that exist have been instituted by God. 2 Therefore whoever resists the authorities resists what God has appointed, and those who resist will incur judgment.