Last Friday, Edwin Ramirez-Mejia’s aunt drove from her Miami Beach home to her nephew’s Miami apartment. The two planned to discuss a family-run business in Guatemala, police said.

Instead, they argued, according to police — Ramirez-Mejia’s anger so intense that he cut off his aunt’s head, put it in a bag and threw it and the body in a trash bin outside his apartment.

“During that encounter, he ends up decapitating his aunt,” said Eddie Rodriguez, executive assistant to Hialeah’s chief of police. “He ends up cutting off her head.”

By Monday morning, Rodriguez said, when the garbage was collected in Miami and driven to a plant in Hialeah, the body and head of Silvia Karina Castillo Castillo, 37, had separated. Workers at Hialeah plant called Waste Connection discovered her headless corpse and called police.

“She went to Mejia’s house in Miami Friday after work to discuss a business in Guatemala,” Rodriguez said.

Karina Castillo Castillo’s badly decomposed headless body, found on Monday, immediately turned into a whodunit-and-why for detectives. They quickly pieced together the crime after contacting other police departments about missing persons.

Ramirez-Mejia, 27, was arrested late Wednesday night and charged with second-degree murder and abusing a dead body. He was taken to the Turner Guilford Knight correctional center. By Thursday morning, no bond had been set.

Rodriguez said the deadly and gruesome encounter began after work Friday when Karina Castillo Castillo left her Meridian Avenue apartment in Miami Beach and headed to her nephew’s first-floor pad at 1035 SW Fourth St. in Miami.

They were going to talk business, Ramirez-Mejia told police, until something went terribly wrong and the woman’s head was removed from her body. Police still hadn’t said by Thursday how Ramirez-Mejia cut off his aunt’s head.

They did say that after giving formal statements, he confessed. And he told them that he put his aunt’s head in a bag and put both the head and the body in a dumpster outside the Miami apartment.

Once the body was discovered in Hialeah, Rodriguez said, detectives called other policing agencies and soon discovered Silvia Karina Castillo Castillo had been reported missing. Rodriguez said family members, including Ramirez-Mejia, went to the Hialeah Police Department and were questioned.

Under questioning, according to Rodriguez, detectives began to notice discrepancies in Ramirez-Mejia’s statements.

“He gave conflicting statements,” Rodriguez said. “Then he confessed.”

Rodriguez said Ramirez-Mejia also told detectives that he and his aunt were in the U.S. illegally. Rodriguez hadn’t confirmed that by Thursday morning, saying background checks on Ramirez-Mejia and his aunt had come back empty.