Marcos Santana Andújar, president of the Network for the Rights of Children and Youth of Puerto Rico Youth rights group expresses deep sorrow over the death, urges reflection on how to prevent violence affecting children and youth By THE STAR STAFF Authorities on Thursday were investigating a death of undetermined cause involving a minor that was reported around 6:23 p.m. on Wednesday at the old sugar mill in the municipality of Arroyo. According to the police report, a call to the precinct…