When people are deeply involved with organized crime, talking to police in any capacity is pretty much a death sentence. Providing police with information, any kind of information, will get a person branded a rat. Gangs are absolutely ruthless when it comes to "snitching". It won't be a quick head shot, you're dead, kind of death, either. We all know the examples that cartel members and their associates make out of people who cooperate with LE.
In any case, I'm not surprised that the brother and husband are holding back. Of course I wish they weren't, but there are probably very complex associations at play here. If the men are associated with organized crime, and it was announced to the public that they were "cooperating fully", their lives would be in danger. Even their own gangs (if affiliated) would see them as huge liabilities. Even if it were in relation to a rival gang member, it doesn't matter. Gangs won't tolerate it.
I'm not saying it's right, but I think this case is complex and requires a bit of nuance. I was under the impression that Luis turned over the POI's photo to police voluntarily. Maybe police are keeping more secret in an attempt to protect them. I'm sure there's lots of information the men could give them, if they are in fact affiliated with organized crime and involved in high scale narcotics trafficking. That's why I thought it was particularly telling that Luis provided police with the information that they needed to find the POI. I believe it came to a point where he was willing to take the risk.