FALL RIVER — The state medical examiner's office is conducting an autopsy into the fatal police shooting of a 19-year-old New Bedford man and prosecutors will not say what caused a Fall River officer to shoot and kill the teen.

The medical examiner's office is performing an autopsy into the death of Larry Ruiz-Barreto, who lived in New Bedford's West End, but has not determined the cause of death, according to Gregg Miliote, a spokesman for Bristol County District Attorney Thomas M. Quinn III.

The teen was shot and killed shortly after 11:35 p.m. Sunday as he was fleeing the area of Airport and Riggenbach roads near Fall River's Industrial Park, the DA's office said. Fall River police responded after receiving a 911 call about possible gunshots being fired in the area.

A number of vehicles were leaving the area and an officer attempted to stop a vehicle driven by Ruiz-Barreto, prosecutors said. An officer fired shots into the vehicle, hitting Ruiz-Barreto. The teen was transported to Charlton Memorial Hospital in Fall River and was pronounced dead a short time later.

Miliote would not answer a number of questions on Tuesday, ranging from whether the New Bedford teen was armed with a gun, did he drive his vehicle at the officer or was the Fall River officer endangered somehow when he decided to use deadly force.

"We're conducting a thorough investigation of all the facts before, during and after the shooting," he said. "We're not going to comment on things as we find them. When our investigation is complete, we will issue a very thorough report."

The Herald News of Fall River, quoting a source close to the investigation who is not authorized to speak publicly about the probe, said the initial investigation indicates that Ruiz-Barreto drove his vehicle at the officer.

Family members told a Boston TV station on Monday there were no guns at the scene and sounds believed to be gunshots were really sounds from cars racing.

Karl Hetzler, chairman of the Fall River Industrial Park Association, said the area has attracted racing for decades, though he added it had not been a recent concern for the businesses in the park. Hetzler said he expects racing to be a topic of discussion at the association's next meeting in a couple of weeks.

"No matter what time of day or night it is, we want to believe that our employees who are coming and going from the park are going to be safe," said Hetzler, who added that he hopes recent events will prompt increased police presence around the park to curtail drag racing and other illegal activity. Hetzler said the industrial park previously discussed with the Fall River Police Department the possibility of putting surveillance cameras at the entrances, exits and main roads, but he said the cost at the time seemed to be prohibitive.

Several people at the family's home said they were unaware of the family's wishes and declined to speak with The Standard-Times on Tuesday. Ruiz-Barreto's stepmother, Leslie Lugo, later said the family has been advised by their attorney not to speak with the media.

The DA's office knows the name of the officer who fired and killed Ruiz-Barreto, but is not releasing the name.

It is difficult to pinpoint when the investigation by prosecutors and state police detectives assigned to the DA's office will be finished, Miliote said. Witness reports have to be compiled as well as lab and ballistics reports. 

Officer-involved shootings can take anywhere from several weeks to months, Miliote said. 

"Every investigation is different. Wherever the investigation leads us that is where we will go," he said. "Every case is unique. It will take as long as it takes."

Follow Curt Brown on Twitter @CurtBrown_SCT. Brian Fraga of The Herald News contributed to this report.