In cases like this the local police usually know who to go after and whose heads to crack. I've seen some of this happen here in the DR and most police are a lot more savvy than you give them credit for. My experience is they just don't go out and randomly knock heads. They know their community and who is usually behind criminal activity.
And when they do not have any background information or any suspects, they will arrest everybody in the vicinity in the hopes that someone will talk. Those that are not involved are usually let go right away. With a population that WILL NOT TALK to police investigators this is about the only way the police can obtain information about a crime. I've seen this happen when the crimes are serious, such as murder or a violent attack on a tourist or foreign resident. I've also seen the same cases solved because of information gained from this type of police activity. It's an unfortunate tactic for those involved, but it works.
And when they do not have any background information or any suspects, they will arrest everybody in the vicinity in the hopes that someone will talk. Those that are not involved are usually let go right away. With a population that WILL NOT TALK to police investigators this is about the only way the police can obtain information about a crime. I've seen this happen when the crimes are serious, such as murder or a violent attack on a tourist or foreign resident. I've also seen the same cases solved because of information gained from this type of police activity. It's an unfortunate tactic for those involved, but it works.