The family of Nolan Wells, a Mississippi teenager who was found dead after going missing last weekend, is demanding answers about what happened to him.

Wells, 18, did not return with friends from a boating trip to Horn Island on 4 July and his body was found in the water two days later.

The Jackson County Sheriff’s office said “no foul play was suspected” but is calling on the public to come forward if they have any information.

Civil rights attorney Ben Crump – who has been hired by the family – says there have been conflicting witness statements and that he has ordered an independent autopsy.

An initial autopsy was carried out earlier this week, but the results have not been released. Dental records confirmed the body was Wells, Jackson County coroner Bruce Lynd told the BBC’s media partner CBS News.

His mother, Christine Wonsley, was the first to raise the alarm that her son, who played American football at Southwest Mississippi Community College and was described by his coach as a “happy-go-lucky kid”, had gone missing after he did not return on the evening of 4 July.

Authorities discovered his body off the coast of the island on 6 July, following a search that included multiple local, state and federal agencies.

National Park Service described Horn Island as having “no staff, drinking water, shelter, facilities, or communication”.

“They [Wells’ family] have serious, unanswered questions about the circumstances that left Nolan alone on the island and about how he died,” said Crump.

He has questioned what he says are conflicting reports about whether Wells left the island with friends or whether he stayed behind.

Christine Wonsley and Nolan’s father, Elmore Wonsley, told CBS Mornings that they don’t believe their son would have decided to stay back on the island by himself.

“That’s not in his character,” said Elmore Wonsley.

The Jackson County Sheriff’s Office has put out a press release “asking anyone who was on or near Horn Island on July 4” to contact the department and also requested any original, unedited photos and videos of “alleged altercations” or images of Wells.