Witness statements contained in a police affidavit filed in Hilo District Court this week describe murder suspect Vernon E. Costa "as a little man with a big chip on his shoulder" who was obsessed with his ex-girlfriend.

Costa, 41, of Mountain View, is accused of repeatedly ramming the car that 20-year-old Janelle Nardin was riding in during a high-speed chase Sunday on Mamalahoa Highway. The pursuit ended in a crash that killed Casey Ann Swain, 35, and Pua Santa-Isabel, 26.

Police said the women were in a 1987 Honda sedan that was traveling at speeds of up to 100 mph to escape Costa, who was in a 1998 Dodge Dakota pickup.

Costa was arrested Monday and is charged with first-degree murder, two counts of second-degree murder, attempted second-degree murder, two drug charges and six traffic charges, including driving while his license was revoked.

An affidavit filed Thursday said Nardin told investigators that she had tried to break off her relationship with Costa but that he kept harassing her and following her. She said he had threatened her, beaten her and any man she was with, gave her a black eye, pulled her hair and choked her until she was unconscious.

"She said she was sick of it and she was sick of Costa," said a report by Detective Mark Haggerty.

In fact, Nardin filed for a temporary restraining order against Costa in February, but it was dissolved two weeks later.

Nardin told Haggerty she had been "hanging out" for several days in Kona, staying at Swain's house. The younger woman wanted to go partying in Hilo and called an acquaintance in Waimea at about 10 p.m. last Saturday to ask another friend to pick her up. Costa was at the house and "had been going off" thinking the acquaintance was hiding Nardin, according to the acquaintance's statement to police.

The three women drove to an unnamed scenic point where they thought they would be meeting the friend, but instead they spotted the Dodge pickup truck with the driver hunched behind the wheel. When Nardin realized it was Costa, they sped off with the truck in pursuit.

Nardin told Haggerty that Santa-Isabel was driving and the other two women were sharing the front seat with her. Nardin said she told a frightened Swain to get in the back and fasten her seat belt. Nardin said she recalls buckling her own seat belt but doesn't know if the other two women were fastened in.

As they raced toward Waimea at around 12:10 a.m., Nardin called 911 to report that Costa had rammed their car several times from the rear. She told Haggerty they were afraid to stop because Costa would hurt her.

When the Honda crashed near mile marker 16, Swain and Santa-Isabel were thrown from the sedan. Costa pulled over and flagged down a motorist to take him and the injured Nardin to the North Hawai'i Community Hospital in Waimea.

Hospital staff told police the two arrived at the emergency room with Nardin, her bleeding head wrapped in a towel, crying out "I don't want to die! Don't let me die! Please help me!"

When Nardin was taken in for treatment, Costa left.

Nardin received stitches in her head and was in severe pain, the affidavit said. She told Haggerty she didn't remember the accident or how she got to the hospital. The detective noted in his report that she seemed "evasive" and did not react when told her two companions were dead.

During a search Monday afternoon, police found Costa in the Eden Roc subdivision in upper Puna. He had a broken nose and ribs and other injuries, the apparent result of a beating.

A 38-year-old man was detained as a suspect in the assault. He was released and has not been charged. According to the police affidavit, the man told Haggerty he had met Costa only once before, when Costa came over to the man's house asking questions about Nardin. The man told the officer "he didn't like the way Costa was pushing his weight around" and kicked him out with a warning not to return. He "said that Costa is a little man with a big chip on his shoulder."

The man said he told Swain, his girlfriend, not to go to Hilo with Nardin, and Swain promised she wouldn't. He went to bed around 10 p.m. Saturday, and when he awoke Sunday morning, Swain was gone.

Detectives are still trying to find the motorist who drove Costa and Nardin to the hospital. Anyone with information should call Haggerty at (808) 326-4646, ext. 277; the nonemergency telephone number at (808) 935-3311; or Crime Stoppers at (808) 961-8300 in Hilo or (808) 329-8181 in Kona.

Reach Christie Wilson at cwilson@honoluluadvertiser.com.