When Brandon Brei GRD ’06 was an Eagle Scout in middle school, he went to Philmont, a Boy Scout ranch in New Mexico. The troop was on a two-week survival mission for which they had to carry their food and supplies in backpacks. But even though Brandon’s pack was heavy and he had far to hike each day, he was eager to help his fellow scouts, said Brandon’s father and scoutmaster, James Brei.

“Any one pound weight in your pack was like 10 pounds when you’d been hiking for 50 miles,” James Brei said. “But we had some kids that were on the smaller side, and Brandon would go over and take things out of their packs and put them in his. That was the kind of kid Brandon was even then.”

Brandon, who was quick to help others throughout his life, drowned Saturday in a swimming accident on a Yale-sponsored trip to Puerto Rico. Brandon was trying to save another student, Epidemiology Professor Durland Fish said. Brandon was 26 years old. Friends and family remembered Brandon’s sense of humor, selflessness and devotion to his work.

The students were on a training trip to study Dengue Fever at the Center for Disease Control’s laboratory in San Juan. Fish led the trip; the 10 students were from the Graduate School and the Department of Epidemiology and Public Health.

Last Saturday, the the group went to Cabeza Chiquita beach on the northeast coast of Puerto Rico. The destination was recommended by tour books and passers-by, students said.

“The place that we were at didn’t appear to be a very dangerous place,” Fish said. “It was a beautiful, pristine beach with only a few people on it.”

While swimming, five students — including Brandon — encountered trouble in the water, Fish said. Two were able to make it back on their own and two others were rescued by a skin diver after they clung to submerged rocks for 20 minutes, Fish said. Brandon disappeared near the rocks, Fish added.

“Brandon was lost as a result of trying to save another student,” Fish said. “We all admire him for that courage.”

The skin diver, Jesus Rivera Velez, was not swimming in the water because it was too rough, Fish said. But when he saw Brandon disappear, Velez realized the other two clinging to the rocks were not going to make it, Fish said. Two people independently asked him not to go.

“We didn’t want to lose anyone else,” Fish said. “He said he had to go — he swam out and brought back the first person. He brought back the second person just as they let go of the rock and he just barely got back with the second person. He was the second hero of the story.”

The local police department came, but could not get close enough to the rocks, Fish said. The Coast Guard searched during the rest of the day and night, using helicopters and equipment to track the current to know where to search. They called off the search on Sunday afternoon, Fish said.

“The Coast Guard gave us a presentation on their efforts,” Fish said. “There’s no chance that they would have missed anybody out there.”

Noel Brei, Brandon’s mother, said she saw pictures of the beach where the accident happened.

“I’m happy that he was at a beautiful setting,” Noel Brei said. “I know accidents happen –. He loved being outside. I think he just really appreciated nature.”

Fish said he took photos of the students working in Puerto Rico and Brandon is in most of them — closest to the action.

“I think he enjoyed the field trip,” Fish said. “It’s the kind of work that he really loved to do.”

Brandon’s mother said her son’s altruistic instincts were what got him interested in public health.

“I think he wanted to find cures for diseases and make the world better,” Noel Brei said.

Fish said Brandon’s doctoral thesis addressed the issue of how pathogens are maintained in nature.

John Brownstein EPH ’05, who went on the Puerto Rico trip and had known Brandon since Brandon arrived at Yale in 1999, said Brandon was brilliant but never acknowledged it because he was so humble.

“He would be able to turn people’s papers that were a mess and look at them and turn them into something important,” Brownstein said.

Brandon applied the same critical eye to other things as well, friends and family said. Brandon’s father said one of Brandon’s recent accomplishments grew out of a nature program James talked his son into watching while they were on vacation together. Brandon found fault with some of the program’s facts.

“All of a sudden Brandon just got red in the face,” James Brei said. “I was just kind of kidding around, and I said, ‘Well, write and tell them it’s wrong.’ And he said, ‘Well, I’m going to do that.'”

Brandon wrote a letter to Science, a premier scientific journal, which published an article that was the source of the facts he disputed. Friends said Brandon “tore up” the article’s arguments based on his own research, and the authors of the original article retracted the findings he criticized. Brandon’s rebuttal will be published in the journal.

“It was just kind of the thing, you know — he saw something and … it was wrong, and he just assumed we were all so interested in [the program], that wool was being pulled over our eyes,” James Brei said. “Brandon took it professionally as heresy or whatever, and that’s how he got on track of getting published.”

Brownstein said Brandon worked on his letter for two weeks, crafting it meticulously.

“Everybody around him was being negative, but Brandon wouldn’t listen,” Brownstein said. “He wanted to do it and he wanted to do it absolutely right.”

Hannah Gould EPH ’06, a friend of Brandon’s who also went on the Puerto Rico trip, said Brandon asked her to read the letter before he sent it. She only suggested the slightest correction.

“I don’t think I’ve ever read anything so beautifully written,” Gould said.

Lindsay Mitchell ’03, an MCDB major whose senior research project is a continuation of Brandon’s research on the transmission dynamics of Anaplasma phagocytophila, the agent of Human Granulocytic Ehrlichiosis, said Brandon helped her with every stage of her experiment. She said he taught her “virtually everything” she learned in the lab this year.

“As a scientist, Brandon was impeccable,” Mitchell said in an e-mail. “As an advisor, Brandon was selfless. As a person, Brandon was full of life and quick to smile.”

Brandon’s two younger sisters recalled his sense of humor.

“Brandon could always make me laugh,” his sister Amanda Brei, 21, said. “He was just such a fun brother. He was definitely such a role model for me, because anything he did, he did at such an impressive level. He was basically all that you could ask for in a big brother.”

His other sister Michelle Brei, 24, agreed.

“He was my hero from my earliest memory,” Michelle Brei said.

–The Associated Press contributed to this report