Bailee Lynn Rios is set to face two second-degree murder charges over a Los Angeles bus collision that killed two passengers, according to prosecutors cited by ABC News Australia.

Prosecutors allege that Rios, 36, was under the influence of drugs when she swerved into the wrong lane, ran a red light and struck another vehicle before crashing into the bus. The victims were identified as bus passengers Daniel Castillo, 46, and Gage Weida, 31.

Rios was being held on bail of $US4.1 million ($5.7 million) and was scheduled to appear in court. The source text did not provide details of her legal representation or a response to the charges. Her mother, Cindy Rios, said she was shocked and saddened by the events and had not spoken with her daughter since the arrest.

About two hours after the collision, a news helicopter used by NBC and Telemundo crashed while covering the incident. The crash killed pilot George Marciniw and reporter Eliana Moreno, who were aboard, as well as 29-year-old Edy Gutierrez Mejia on the ground. A fire also damaged at least four cars and two storage containers.

Investigators have not given an immediate explanation for why the helicopter went down. National Transportation Safety Board investigator Fabian Salazar said the final seconds of video broadcast by the crew could provide important evidence. The footage includes an alarm in the cockpit, a woman saying “uh oh” and asking, “You can’t pull up?” before the recording ends as the helicopter descends.

Aviation safety expert Jeff Guzzetti said the alarm could indicate a loss of engine power and a dangerous reduction in main rotor speed. He said the pilot appeared to be attempting an emergency manoeuvre intended to use the wind to restore rotor speed. The NTSB is investigating both the helicopter crash and the bus collision. A vigil was planned for Thursday evening for victims of both incidents.