The incident happened around 2 p.m. Saturday on a beach in Jaboatao dos Guararapes, a city on the eastern edge of the country.
Marcelo Rocha Santos, 51, had been drinking there with a friend when he felt the need to urinate, so he waded out into the water to do so.
Ademir Sebastiao da Silva, who was also at the beach, says he went out with Santos to relieve himself at the same time.
“As the beach has no bathroom, I went into the sea to pee,” he said. “I was beside him with the water up to our waists.”
“There was a lot of blood in the water,” said Edriano Gomes, who was at the beach with da Silva during the attack.
Santos’ friends ultimately jumped in and pulled him back to shore. Graphic photos posted online show that Santos lost part of his arm and a chunk of his leg in the attack.
He was rushed to hospital, where he was pronounced dead.
The ocean was cloudy and turbulent at the time of the attack, which would have made it hard for the victim to see the approaching shark.
Da Silva said he’s still rattled after witnessing the attack up close.
“It could have been me,” he told Brazil’s Globo News. “If I had been diving or lingered in the water, I could have been attacked.”
A lifeguard was reportedly on duty at the time but was not able to intervene.
Rodrigues says the bite marks indicate that the tiger shark was roughly 2.6 metres long.
Local officials later pointed out that the beach has a history of shark attacks, and that signs are posted to warn swimmers about the danger.
There have been more than 60 shark attacks in the area in recent decades, including 25 other fatalities since 1992. A dozen previous attacks have been reported at the beach where Santos was killed, according to state data.