Collecting evidence
The police took pictures of all of the names that they saw on the ledge. They had been chiseled in with some sort of pocket knife or sharp rock. The names matched the ones that were from the group of teen boys they suspected to be the culprits. It was too good to be true.
The only problem was that the names were nicknames for each of the boys and it was still going to be difficult to link them to this. Although it was now obvious who had committed the crime. The police needed the boys to admit it or else they would not be able to press charges.