My little advice for WITNESSES and story about dealing with criminals

Many of you already knew the story from me but I will still post it here anyway...

I've been studying in criminology area and learning a lot from them... It opened my eyes to be witnessing many situations by then...

But... I think I am myself into a lot of situations rather than just being a witness...

Here's a long story that I posted somewhere else, with my own advice at the end, for those who are witnesses of crimes...

Few years ago, 3 groups of black guys were attempting to steal my brother's car... Since my brother's car has illegal black tinted windows all over, I couldn't see well but enough to see 3 heads inside the car (it was during the day, not night)... There was 3 attempts of starting the car... So I was like "Alright, what the hell is going on..."... I just went to take a look, thinking that I would be talking to my bro... But as I opened the door, I saw 3 black guys inside the car so I was like "Hey"... I didn't panic... All of them just stepped out of the car at the same time with some huge eyes... I knew they were street gangsters since I had few of their co-members being my apprentices and I just happened to see their faces when there was about 100 black people in the streets with chains, knives and baseball bats but not even a huge pool of blood... Anyway, about the 3 guys, I asked them what they were attempting to do, just like that... They looked at each others and said "Our man told us it was this car, right?" one other was like "Yeah!" and the other one, "True"...
I just went like "Well, it's not the right car. Just don't ever come back here to touch it again when there's plenty of other cars around here."... They were like "Ok" and they were about to leave... I said louder before they completely left "WHITE CIVIC 24TH AVENUE..." (A type of car and the name of the street)... That car was the car of a Vietnamese guy who's been making sh*ts on me... I knew about his life, cars, etc all along but I've never decided when to strike back a huge revenge... So, by knowing how his car could be so easy to steal for people of the same type I caught (the 3 black guys), I just told those guys about it... Later, I've realized the car was no longer there for months... I'm glad it was a free service for me and also a sort of profit for those who stole the car easily... That Viet guy has understood my message...

Later... Those 2 of the 3 black guys I caught, I've met them randomly in a bus, they were going to schools just like normal guys... I could say I've earned a lot of respect. I thanked them for understanding my message and they thanked me back because they've realized they wouldn't probably be in school by now if I wasn't being cool... Me, even though I'm nothing THAT much related to Yakuza, Triads, Mafia, Street Gangs or whatever (unless it's for comedy), I've been having enough experiences to the point that I know exactly how in deep sh*t you could be if you call the cops in the wrong situation. I know you can think it's selfish for not saving the society but YOUR family can be put in a lot of trouble, innocently involved though you attempt to do something to protect the society (in fact, you only protect a small part of the society but it may not stop the hemorrhage if you know what I mean).
It's GOOD ONLY depending on certain situations, and even better when you are in a society where there's not much of gangs and bad organizations...

When you're a witness of a crime or just a crime attempt, just be careful. Be ANONYMOUS as much as you can, especially when you contact the cops. Police should understand about your anonymousness and should respect that unless it's some crooked cops. Up to you to trust or not trust. A witness can become a hot target. Just make sure you're out of the target. "Coolest" thing is that many witnesses themselves don't even know there's a target drawn behind their head...