If God is telling you just to pray, then do it, but sometimespeople refuse to do anything and use the excuse that the "don't want to play God" when in fact they are nothing but aiders and abetters of crimes, whom God would like to use to report it and help put an end to it instead.
We just need to do it in the way God wants. And it sounds like you hve done so, telling your friend of these dangers. Every situation is different. It's just important for us to remember that God chastened Moses for saying "Who am I?" becasue He wanted Moses to do soemthing.
As I say, though, that doesn't appear to be true in yoru case; I just got back from a seminar where some stuff was discussed that wss pretty bad as far as what people do. So, this is just as a general reminder to all of us to obey God and let Him handle things, but to be willing to step in if He leads. And, I strongly believe that most on here would step in if He led, but some of the xcuses mentioned there that people make just made me feel led to mention this somewhere.
John 3:16 (KJV) For God so loved the world, that He gave His only begotten Son, that whosoever believeth in Him shall not perish, but have everlasting life.