An employee of Mexico's Tijuana Fire Department is being investigated for the killing of a Chula Vista woman and her friend, officials confirmed.

Roxana Diaz, 32, and her friend, Roberto Carlos Morales Trujillo, 39, were fatally shot on the morning of Aug. 16 in an area called Canon Union, less than five miles northeast of Playas de Tijuana, a popular destination in Baja California near the U.S.-Mexico border.

Diaz was transferred from a hospital in Tijuana to UC San Diego Medical Center where she later died, her family told Telemundo 20.

Trujillo was shot twice in the abdomen and was found dead on a street in Playas, law enforcement officials said.

The Secretary of Public Security in Tijuana, Marco Sotomayor, said three men were arrested in a toll booth in Ensenada in connection with the killings.

When officials arrived at the booth, a woman who was with the trio and a girlfriend of one of the individuals, told investigators she was allegedly being held against her will. She told them of the slayings of Diaz and Trujillo in Tijuana.

According to Tijuana police, the three men who were arrested are brothers and firefighters who work for the Tijuana Fire Department. The three suspects are 29, 31, and 32 years old.

The brothers will face charges of deprivation of freedom. At least one of the men is being investigated directly for the killings of Diaz and Trujillo.

Officials believe Trujillo was the ex-boyfriend of that suspect's current girlfriend.

"In a fit of jealousy, [the individual] pulls out a gun and shoots the victims, killing his girlfriend’s ex-boyfriend and the young woman who later died," said Jorge Álvarez Assistant State Attorney, offering a glimpse into a possible motive for the killings.

Tijuana Fire Department Capt. Juan Carlos Fuentes spoke with Telemundo 20 Thursday and said he and the entire department were in utter shock over the allegations against three of their own.

Fuentes said the news left him feeling sick, with a knot in his throat.

The captain described the three suspects as quiet, promising young men who, before this, had a real future with the fire department.

"I met them when they were kids," Fuentes said. "Their parents taught me and I taught them."

The captain said he would've never imagined his colleagues would've been tied up in something like this, with one accused of homicide.

Fuentes said the brothers had a lot of family ties to the fire department.

If the accusations are true, the captain said the suspect accused in the killings made a horrible decision that "ruined his life."

Tijuana Fire Department officials said the arrest of the three firefighters has made the community look at their agency in a negative light.

"They look at us differently; I've experience it," he explained.

Meanwhile, Jose Luis Jimenez, director of the Tijuana Fire Department, said the agency is taking action to ensure an incident like this never happens again.

He said that, as firefighters, his crews witness traumatic situations daily first-hand, and he worries their line of work takes a heavy toll psychologically.

Jose Modesto Calleja, a retired member of the Tijuana Fire Department, told Telemundo 20 he thinks this case is an "isolated" incident.

"These young men were good young men," he said. "They're still good."

Officials at the Tijuana Fire Department have already begun an internal process to dismiss the three suspects from their positions. The names of the firefighters under investigation were not immediately released.

Back in San Diego, friends and family are mourning the sudden loss of Diaz. Friends described her as a happy person and hard worker.

Her family said she worked at a KFC restaurant in Chula Vista and leaves behind a 16-year-old son. Diaz's uncle, Francisco Corral, told Telemundo 20 Diaz worked hard to build a good life for her son.

He said Diaz traveled often to Tijuana to visit her mother, and said the victim's mother is devastated by the slaying. Corral said Diaz's family isn't sure if she was even the intended target of the suspect.

An online fundraising page has been created by family members on behalf of Diaz.

Editor's Note: An earlier version of this story stated the killings happened in Playas de Tijuana; we have since learned the crimes took place in Canon Union, an area about five miles northeast of Playas.