NEW YORK — Attorneys for the family of a Mississippi 18-year-old who was found dead after a July 4 boat trip with friends to an island off the Gulf Coast called for a deeper investigation and greater transparency at a news conference Friday with the Rev. Al Sharpton, saying many of the details they’re discovering are “not adding up.”

Noted civil rights attorney Ben Crump, who was retained by the family of Nolan Xavier Wells earlier this week, has said the family has concerns about the investigation and planned to conduct an independent autopsy. Wells travelled by boat to Horn Island, Mississippi on July 4 with a group of friends, but did not make the return trip with them that afternoon. His body was found early Monday morning, more than a day later.

While Jackson County Sheriff’s Office officials said investigators don’t suspect foul play in the Black college student’s death, the sheriff has asked for any witnesses or people with video from the popular beach island about 10 miles (16 kilometers) off the coast of Mississippi to come forward to help shed light on the moments before Wells’ disappearance and death.

Family members have raised concerns, saying they’ve seen video of a fight allegedly involving their son, and saying as an elite athlete he was able to swim. Wells, who would have turned 19 next month, attended Southwest Mississippi Community College, where he played wide receiver on the football team.

At the news conference Friday attorneys said the friends who left Wells on the island, took his phone and keys when they departed. Crump said Wells’ family used an app to track his phone, and a friend went to where it was on land to pick it up.

“What teenager would leave their phone behind if they’re going to stay on this island? What teenager wouldn’t take their phone? It’s not adding up at all,” Crump said.

He added that the family believes text messages from social media apps had been deleted from his phone when they got it back, and they plan to employ experts to try to receive all the data they can.

A photo posted to social media, allegedly from the boat ride to the island, shows Wells with his arms around three white, male friends. Speculation and suspicion about the teen’s death have been rampant online, as people grapple with the state’s history of racial tension and what it means to be a Black person in a majority white space.

Wells’ mother, Christine Wonsley, looked to the sky several times as lawyers spoke Friday, to hold back tears. When she spoke, she said this was not how she wanted the world to know her son.

Wonsley said they had taught him about history, but he was a peacemaker who didn’t like division, and wanted everyone to be included.

“We just wanna know what happened,” she said, through tears. “And why our baby didn’t come home.”

Crump called for a thorough investigation, saying to law enforcement, “They want to know that you have not taken the path of least resistance.”

“If the roles were reversed and you had three young Black men on a boat with a young white man and that young white man ended up dead, what kind of investigation would be conducted by the Mississippi law enforcement officials? How many times would those three young Black men be interrogated?” he added.

It’s the second case the noted civil rights attorney has taken on in the state in recent months. He also was recently retained by the family of a Mississippi 1-year-old who was killed when police fired into a moving car.

Jackson County Sheriff John Ledbetter said earlier this week that Wells’ mother had called to report him missing around midnight into the morning of July 5. Crews from multiple local and state agencies began an extensive search Sunday of the island and surrounding waters. His body was recovered early Monday, family members confirmed.

An official autopsy was conducted Tuesday, though officials have said it could be weeks before results are released. Ledbetter said Wells’ friends were cooperating with the investigation.

“From the people we’ve talked to, it sounds like he chose to stay on the island with the assumption that he was going to ride back to the mainland with someone else,” Ledbetter told The Associated Press earlier this week.

Crump and Wells’ family said some of those details didn’t seem to add up either, saying from the videos they had seen Wells was one of, if not the only, Black person on the island where there were around 200 people celebrating the holiday. They said the girl the friends said Wells was speaking to gave a different story about him leaving with those friends. They raised questions about why no one would have given him a ride home if he chose to stay.

“If he’s drowning, nobody sees him drown? Nobody offers assistance? Nobody tries to help? I mean, obviously he stands out. I think he’s the only Black person I saw when I’m looking at the videos,” Crump said.