Police have initiated a negligent homicide investigation into the death of an 18-year-old passenger in a single-­vehicle crash in Hauula.

The victim’s name has yet to be released by the Honolulu Medical Examiner’s Office.

A Hauula resident who declined to disclose her name said the victim was a senior at Kahuku High &Intermediate School and was related to the two other occupants of the vehicle.

At about 4:20 a.m. Tuesday, police said, a silver Toyota pickup truck was traveling east on Hauula Homestead Road when it skidded a few hundred feet and struck a large tree at a bend in the roadway.

The vehicle flipped over upon impact, said Lt. Andre Peters of the police Traffic Division.

A resident who lives near the crash site said she heard a “boom” and thought it was a falling tree.

Fifteen firefighters responded and used tools to extricate the three occupants, who were trapped inside.

Emergency Medical Services transported the 18-year-old man — the front-seat passenger — in critical condition to Kahuku Medical Center, where he died.

Paramedics also transported the driver, a 27-year-old man, and a passenger, a 22-year-old woman, to The Queen’s Medical Center in critical condition. Peters said their condition was later upgraded to serious.

Excessive speed and alcohol were factors in the crash, police said. The speed limit in the area is 25 mph.

Peters said none of the occupants was wearing a seat belt.

In addition to the negligent homicide investigation, police also have initiated a negligent injury investigation.

This is the fourth traffic-­related fatality of 2018 on Oahu, compared with one at the same time last year.

Area residents say speeding has been a problem on Hauula Homestead Road and recommend speed bumps be installed.