Another, empty envelope was discovered on the floor of the car where the two victims were found, according to El Nuevo Dia, a Spanish-language Puerto Rican daily.
Only $11 was found on the 31-year-old officer, who family members say had taken out large amounts of cash before heading to a bar in the town of Cerro Maravilla with his 21-year-old sister, Yazmín Plaza Otero.
Yazmín allegedly got into a heated argument with an unidentified woman at the bar before she left with her brother. Aviles was visiting the island to persuade his sister and mother to relocate to Miami to help his wife, who is also a Miami-Dade Police officer, babysit their 17-day-old twins.
According to El Nuevo Dia, Yazmín was recently visited by court officials relating to "a case of aggression against a sister."
She also had a stormy relationship with her boyfriend, who might have mistaken her brother for a new boyfriend, according to the paper.
The siblings were found in a gray 2009 Toyota Corolla that Aviles had rented. The keys were in the ignition, but the lights and engine were off.
It was on a hilltop in Cerro Maravilla that two pro-independence activists were gunned down by police in the '70s. A heated election is looming on the island, but it is not clear whether the argument that erupted at the bar was political.
According to NBC Miami, Aviles was a whistleblower in a state case against Wackenhut Security Systems. The company, now called G4S, was accused of overbilling Miami-Dade County for security services at Metrorail stations in 2006.
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