(CNN) -- A 25-year-old woman from Seattle, Washington, has become the fifth person to die from burns suffered when her fiance's uncle invited them to his house in Puerto Rico and allegedly set them afire.
According to a website set up by friends of the couple, Kate Donahue, 25, died Thursday at Jackson Memorial Burn Center at the University of Miami, in Florida, where she and her fiance had been flown for treatment. Her fiance, Jesus Sanchez, died earlier in the week.
Donahue worked at Group Health in Seattle; Sanchez was an engineer at Boeing.
"They are very much in love," Donahue's mother, Michelle, told reporters when they were first hospitalized. "Their last words before they were intubated were for each other. She loves him, he loves her and the last six months have been the happiest time of her life and the most important thing is love."
The couple had traveled to Puerto Rico so that Sanchez could introduce Donahue to his relatives.
"I got a text from her on New Year's Eve telling me 'Happy New Year' and what a wonderful time she was having," Patrice Moore told a reporter about her niece, Donahue. "And that was the last thing I heard from her."
The next day, Donahue and Sanchez were among 13 dinner guests at the house that Justino Sanchez Diaz shared with his parents and sister in the town of Florida, in north-central Puerto Rico, police said.
But the 45-year-old unemployed furniture mover had prepared for the party by soaking the walls of his house with kerosene and placing kerosene containers in each corner of the dining room, according to Sgt. Frank Perez of the Arecibo Region Police Department's homicide unit.
At about 4:30 p.m, the suspect set fire to the room and the people in it, Perez said. "There was no opportunity for anybody."
Nearly all of those who died suffered burns over 80 percent of their bodies, he said.
Though the suspect had no police record, relatives told police they had long had problems with him, Perez said. He said Sanchez Diaz had burned down a henhouse in the backyard of his brother's home five years ago.
"Many times the family hides their own problems," he said.
The suspect's mother, 83, died, he said. Also dead were his 17-year-old niece, who "died quickly" with burns over 90 percent of her body. Another relative, age 32, was fatally burned, Perez said.
The suspect's father suffered a heart attack the day after the attack. Upon his recovery, he was told that his wife had died, Perez said.
Three other relatives were being treated for burns at the Medical Center of Puerto Rico in San Juan, according to Perez.
Meanwhile, the suspect -- who suffered slight burns that required no treatment -- is being held in lieu of $1.5 million bond in a psychiatric correctional center, Perez said. His next court hearing is scheduled for Jan. 14.