Panama police are investigating the killings of seven young people whose bodies were found in a wooded area near a lake on Saturday.
The victims – four women and three men aged between 17 and 22 – were found near Gatún Lake, 50 miles (80km) north of the capital, Panama City.
They had been in a group of 13 making a trip to the lake. The six who escaped said two armed men had attacked them.
One suspect was arrested.
Forensic tests revealed that all of them had gunshot wounds to the head, local media report.
The bodies were found in a wooded area called Espinar in Colón province. Five of the bodies were in an abandoned bunker and two in separate locations in the woods. Locals and relatives found their bodies on Saturday, two days after they went missing.
The bunker where they were found were used by drug dealers in the past.
Mass killings like the one by Gatún Lake are unusual in Panama.
Earlier this year the country was shocked by the deaths of six children and one adult during an exorcism carried out by religious sect in an indigenous area of the country.