A frantic Janelle Nardin pleaded for help during a cell-phone call to a Big Island 911 operator Sunday, seconds before her car ran off a Big Island highway, killing two women and injuring Nardin.

The 20-year-old woman's 911 calls were released yesterday by Big Island police. Nardin made at least two calls early Sunday morning as the Honda sedan she was riding in was being chased and rammed by a man in a pickup truck.

Killed were Casey Ann Swain, 35, and Pua Santa-Isabel, 26. Nardin's ex-boyfriend, Vernon E. Costa, 41, has been charged with murder.

The first call began with Nardin telling the 911 operator that they were being chased by a car that was "trying to ram us in the back." At first, Nardin appeared composed, but her demeanor deteriorated dramatically during the next five minutes, the calls show.

She told the operator that they were headed to Waimea from Kona and that a "guy was trying to bang us." As she began to panic, the operator attempted to calm Nardin down.

Nardin was able to tell the operator that they were near mile marker 23 of Mamalahoa Highway. But within seconds, everyone in the Honda began to scream and sob.

"We need somebody," Nardin screamed. "He banged us in the back. He banged us in the back. Please, he's going to kill us. Please."

The operator then asked Nardin if she knew who was chasing them.

"Vernon Costa. Vernon Costa," she shouted. "We need help. Please, please."

Just as Nardin identified herself and provided her cell-phone number, the call apparently disconnected. Nardin called back, but much of her call was inaudible.

She did manage to tell the operator that they were close to Waikoloa.

Again the operator asked Nardin who was chasing them. Again Nardin named Costa, according to a copy of the tape released by police.

She then shouted at her friends in the car.

"Oh my god, you guys, he not going stop," she cried.

The 911 tape recorded the moment that the Honda ran off the roadway and plowed into a lava field. The last audible words were from one of the women who screamed, "Oh my god."

That was followed by screaming and the sound of a car crashing. Swain and Santa-Isabel were thrown from the car and died at the scene. Nardin was picked up by a passer-by and taken to the hospital for treatment.

The 911 operator apparently knew what had just happened as she spoke to another operator.

"It's really bad. Oh, it's like really, really bad," she said.

Reach Curtis Lum at culum@honoluluadvertiser.com.