The documents obtained by The Canadian Press also show Marc Wabafiyebazu, son of a veteran diplomat, was brandishing a handgun outside a residence when police arrested him.
"(Wabafiyebazu) stated that he went to the house to steal the drugs while he waited in the car, but then his brother got killed," police say in an arrest affidavit.
"Defendant continued to state that he was from Canada and they had done the same type of thing in Canada and had also done other drug rip-offs in Miami."
Wabafiyebazu, 15, of Ottawa, appeared in a Miami court briefly on Wednesday. The prosecution said a grand jury would consider whether to bring formal felony murder or other charges against him.
Assistant State Attorney Marie Mato said the grand jury could also decide to charge him as an adult.
"If indeed that happens, we will be immediately entering a not guilty plea and defending the case on the merits," his lawyer, Curt Obront, said in an email.
Wabafiyebazu was arrested March 30 after the shooting deaths of his brother Jean, 17, and Joshua Wright, also 17.
Police allege the brothers had gone to a home with the intention of stealing marijuana from a dealer. While the younger sibling waited with the car outside, the older teen went inside.
"In the process of that rip-off, several shots were fired inside of the residence," police allege.
Responding officers found the older Wabafiyebazu and Wright dead inside.
Two other men, including Anthony Rodriguez, 19, the alleged dealer, were wounded and needed hospital treatment.
One witnesses told police she saw the younger brother firing a silver handgun "multiple times" outside the apartment. He was still holding the weapon when police arrested him, the documents state.
Wabafiyebazu remains detained as a juvenile on suspicion of being an accessory to murder, having a firearm as a minor, discharging a firearm in a public place, and for allegedly threatening to shoot an officer in the head after his arrest.
The brothers' mother is Roxanne Dube, a longtime Canadian diplomat who recently became general consul in Miami. Dube attended the hearing Wednesday but did not speak to reporters.
Wabafiyebazu spoke only to answer a few questions from Miami-Dade Circuit Judge Angelica Zayas, who warned him not to discuss the case.
"How are you doing this morning?" Zayas asked him at one point.
"I'm doing fine," he responded.
According to police reports, the Wabafiyebazu brothers — who had only recently relocated from their father's home in Ottawa to South Florida to be with their mother — took her personal vehicle with its diplomatic plates to the alleged drug meeting.
Marc Wabafiyebazu rushed into the house after hearing gunshots, but exactly what he did after that is not clear.
Zayas set an April 20 hearing on the results of the grand jury's work.
— By Colin Perkel in Toronto, with files from The Associated Press.
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