A Canadian diplomat's teenage son accused of involvement in a drug-related shootout that killed his older brother in Florida has been charged with murder and will be tried as an adult.

A Miami-Dade County grand jury indicted 15-year-old Marc Wabafiyebazu on first-degree felony murder charges Wednesday.

Attorney Michael James Corey sits with Roxanne Dubé, mother of Marc Wabafiyebazu, in a Miami juvenile court on Wednesday. Dubé was named Canada's consul general in Miami last November. (Walter Michot/Miami Herald/Associated Press)

Wabafiyebazu, who was being held in juvenile detention, will now be moved to an adult jail to await trial.

Wabafiyebazu's lawyer has said his client plans to plead not guilty to any charges in the case.

Wabafiyebazu was arrested on March 30 after the shooting deaths of his 17-year-old brother, Jean, and 17-year-old Joshua Wright.

Police say the Wabafiyebazu brothers were involved in an alleged marijuana drug deal gone wrong.

The brothers' mother is Roxanne Dubé, a longtime Canadian diplomat who recently became consul general in Miami.

Several shots fired, police say

Investigators 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.

Jean Wabafiyebazu, 17, was one of two people killed on March 30, after what police described as a drug deal gone wrong. (The Canadian Press)

Several shots were fired inside the home, police allege, and Marc Wabafiyebazu rushed into the house but exactly what he did after that is not clear.

Officers who arrived at the scene found the older Wabafiyebazu and Wright dead inside.

Two other men, including Anthony Rodriguez, 19, the alleged dealer, were wounded and needed hospital treatment.

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.