By Seni Tienabeso @seniABC

One student is in custody, another six are in shock after watching a 13-year-old girl being shot aboard their school bus Tuesday morning in Homestead, Fla. And according to The Associated Press, an unidentified male student is in custody for the crime.

"It's traumatic, and now you are going to have to question them and ask them what they saw," said Miami-Dade County police detective Alvaro Zabaleta. "It's a sad situation."

Cops walked next to the bus with dazed students including the 7-year-old sister of the teenage girl who was shot an unknown number of times and airlifted to Miami Children's Hospital, where she died from her injuries. Other officers combed the scene for clues and gathered the students' belongings.

Police have released little information about what they believe sparked this deadly early-morning incident, which happened about 6:45 and just a few minutes away from the victim's school. The shooting occurred on a private bus that was dropping off both elementary and middle school students to three separate schools. Police believe one of the students on the bus brought the weapon onboard but have said little, including whether the shooting was accidental or deliberate.

A firearm was recovered on the scene and all of the students, plus the bus driver, were transferred to the homicide unit, where Miami-Dade County police had to begin the delicate task of questioning the students about what happened. The bus did not have a surveillance camera.

Grief counselors were dispatched to Palm Glades Preparatory Academy, which the victim attended.