HispanicBusiness

The handful of people held in connection with last week's fatal shooting of U.S. Border Patrol agent Robert Rosas are also suspected of running an illegal immigration smuggling operation, authorities say.

The group was in the process of smuggling 21 migrants across the border, according to the San Diego Union Tribune.

The suspected shooter is 36-year-old Ernesto Parra Valenzuela, who was arrested near the vicinity of the killing and was carrying a 9 mm pistol, authorities said.

Valenzuela was arrested on Friday. The next day, four more were detained : Jose Quintero Ruiz, 43, his brother Jose Eugenio Quintero Ruiz, 49, and taxi drivers Jose Alfredo Camacho, 34 and Antonio Valladares, 57, according to About.com.

One of the suspects, Jose Eugenio Quintero Ruiz, is allegedly part of an immigrant smuggling ring suspected of committing two homicides and a rape in the United States, according to the Tribune.

The suspects were detained by Mexican authorities in Tecate area. The FBI had offered a $100,000 reward for information leading to the culprits.

On the night of July 23, Rosas had gone out to check on a suspicious group, and had radioed in for some backup, according to media reports.

When he arrived, the group scattered, and he followed some of the suspects. Other agents said they heard gunshots shortly after losing radio contact with Rosas around 9 p.m. They later found Rosas, who had been shot in the head, according to the AP.

Authorities believe one of the suspects was seriously injured in the struggle and sought medical help, perhaps in the United States. A Silicon Valley news outlet reported that an arrest was made Friday at the O'Connor Hospital in San Jose. The report did not say whether the suspect was Valenzuela.

Although Rosas's death marks the first fatal shooting of a U.S. Border Patrol agent in about a decade, another agent -- Luis Aguilar -- died in January of 2008 when an immigrant smuggler intentionally ran him over with a Hummer.