Gabriel Trujillo, the California graduate student murdered

For four years, Gabriel Trujillo traveled in search of a plant native to the varied climates of Canada, the United States, and Mexico.

The 31-year-old, a graduate student at the University of California, Berkeley, wanted to know why the plant thrived in such a variety of places, and whether the evolution of the species held potential for future conservation and habitat restoration efforts.

However, their investigation was tragically cut short last week in Mexico, where Trujillo's father said he was shot seven times. Authorities discovered his body on June 22 in the northwestern Mexican state of Sonora, days after his fiancée reported him missing, the AP revealed.

The murder has left the family reeling and searching for answers in a case that has once again highlighted the rampant violence plaguing parts of Mexico controlled by drug cartels.

Trujillo crossed the Arizona border into Nogales on June 17. He spoke with his father the next day and he and his fiancée, Roxanne Cruz-de Hoyos, spoke the next morning. He told her that he would go out to collect plants and that he would return to his Airbnb later.

Cruz-de Hoyos was concerned when Trujillo did not return her phone calls and text messages (they usually spoke several times a day) and her Airbnb hosts said her belongings were still there but she had not returned. He bought a plane ticket the next day and flew to Mexico to pick it up.

She was in the wrong place

On June 22, authorities discovered her body about 100 kilometers from the Airbnb. It was still inside his truck, Cruz-de Hoyos said.

She identified him to Mexican authorities as her father rushed to catch a flight from Michigan. Both have received little information about the tragedy and are asking the US and Mexican governments for answers.

“Obviously, I was in the wrong place,” Anthony Trujillo told The Associated Press Thursday as he waited to address a flight home, with her son's remains at her side.

The Sonora state attorney's office said in a statement Thursday that it is reviewing evidence “to establish the facts, conditions, and causes of death”. The statement did not give details about what happened or describe Trujillo's death as a homicide.

His family begged him not to go to such a dangerous place: Sonora recorded 518 homicides through May, according to federal government data. But Trujillo believed that the trip was crucial to his investigation.

Sonora has long been hotspot territory for Mexico's drug cartels, and in recent years those rivalries have escalated the level of violence and, at times, left civilian casualties.

“Gabriel was a passionate ecologist, field biologist, and advocate for diverse voices in science,” the university's Department of Integrative Biology wrote in an email to the campus community. “We all face a world that is less bright because of this loss.”