Authorities and those close to Philipp initially suspected severe food poisoning after the squad ate fish during the trip, before forensic investigators uncovered evidence pointing towards a deliberate killing.
Regarding the suspected motive behind the incident, senior public prosecutor Thomas Hauburger told local media: "We assume that this was an act of revenge."
The arrest sent shockwaves through the amateur outfit, with Rockenberg's head of football Manuel Barufe telling local media: "We are all surprised and shocked. Nobody expected this. We hope the police can fully clarify what happened."