CNN  — 

The sister of the man who drowned while making an underwater marriage proposal to his girlfriend in Tanzania says he was “a beautiful soul.”

Mandy Weber Hoffman said her brother Steven Weber had been planning the unique proposal for his girlfriend Kenesha Antoine for some time.

“The trip had been planned for almost a year, and they were very much looking forward to it,” Mandy Weber Hoffman told CNN’s “New Day” on Monday. “We knew that he wanted to propose to her and he decided that this was the most wonderful time to do it. (It was) the trip of a lifetime, and (he) really wanted to surprise Kenesha with this proposal.”

The proposal

Weber and Antoine were staying in Pemba Island, CNN affiliate WBRZ reports, in a wooden cabin with a bedroom submerged in the ocean off the east coast of Africa.

Weber proposed Thursday by swimming underwater and holding a handwritten note against a bedroom window, according to a video Antoine posted Friday on Facebook.

After the proposal Antoine ran up to the top of the cabin to meet him and embrace him, Mandy Weber Hoffman said, but he never came back up to the surface.

“We don’t know yet if he was injured on the way up, if he hit his head on something or if he had a heart attack,” she said. “We really don’t know all of the details yet, other than he did drown.”

Antoine was unable to reach anyone at the resort where they were staying for help, so she ended up flagging down some passing boaters, who pulled Weber out of the water and tried to revive him. The family is waiting for an autopsy report to get a better idea of what happened to him.

Mandy Weber Hoffman said Antoine is “devastated and distraught”

A cruel twist of fate

During the proposal, Weber placed a note inside a transparent plastic bag that read, “I can’t hold my breath long enough to tell you everything I love about you. BUT…Everything I love about you I love more EVERY DAY!

“Will you please be my WIFE,” the note continued. “Marry me???”

But Weber failed to resurface, Antoine said in a subsequent Facebook post. “You never emerged from those depths, so you never got to hear my answer, ‘Yes! Yes! A million times, yes, I will marry you!!’ ” she wrote.

“We never got to embrace and celebrate the beginning of the rest of our lives together, as the best day of our lives turned into the worst, in the cruelest twist of fate imaginable,” Antoine continued.

“I will try to take solace in the fact that we enjoyed the most amazing bucket list experiences these past few days, and that we both were so happy and absolutely giddy with excitement in our final moments together.”

His sister said he was selfless

Mandy Weber Hoffman said her brother was one of the most selfless persons she had ever known.

“As you can imagine there’s been sibling rivalry all of our lives, but he never ceased to make me laugh. Every time he walked into a room he had an infectious smile and he has a sense of humor that is like no other,” she said. “He’s a beautiful soul that we’re going to miss dearly.”

A GoFundMe page has been set up by Weber’s family to help with funeral expenses.

The investigation continues in Tanzania

The Manta Resort, where the couple was staying, issued a statement on Saturday confirming the death.

“Our sincerest condolences, thoughts and prayers are with his girlfriend, families and friends impacted by this tragic accident,” said Matthew Saus, the resort’s CEO.

Local authorities were investigating, he added.

The State Department confirmed that a US tourist died in Tanzania but gave no further details.

“We offer our sincerest condolences to the family on their loss. We stand ready to provide all appropriate consular assistance,” the State Department said.

CNN’s Emily Dixon contributed to this report.