Jamshidi was kite-surfing at Bois Shadon Beach in the town of Vieux Fort when he took Terrel Joshua Elibos, a boy from the town, out in the water, say police.
The boy fell into the water and drowned around 2 p.m. on Sunday. Police searched for the boy until his body was found at nearby Coconut Bay Beach early Tuesday morning.
It is not yet clear where Jamshidi is from, only that he is a Canadian citizen. Police say he was scheduled to leave the island on Thursday of this week.
No charges have been laid, but Jamshidi remains in police custody and is co-operating with the investigation.
More to come