Irate Phone Call Preceded Slayings : Aftermath: Police try to determine if store owner’s heated conversation with a disgruntled customer is tied to the deadly rampage.

GARDEN GROVE —  The police investigation into the bloody rampage at an auto parts store focused Tuesday on an angry telephone call between the shop’s owner and a disgruntled customer that occurred about half an hour before a gunman killed two and injured four there.

Investigators, attempting to trace the call, believe that Monday’s shooting might have been tied to the dispute with the owner, Charlie Kim, who neighboring business owners say often clashed with his young customers. Kim was wounded in the assault.

Detectives also are looking for any possible links to a homicide in June at a nearby auto accessories store, where a gunman with a similar description shot two customers, killing one and wounding the other. That case remains unsolved and, as with Monday’s shooting, police are uncertain of a motive.

Authorities said they have relatively few clues in this week’s attack. They have no fingerprints or other physical evidence from the scene, and employees said they did not recognize the gunman.

“A lot of these guys are just chasing ghosts,” said Garden Grove Police Lt. Frank Hauptmann, referring to fellow investigators. “We’re still trying to determine a motive, something to explain why.”

The killer fired up to 15 rounds inside and outside the Robotek store Monday afternoon, littering the Brookhurst Street business with shell casings. The number of shots, Hauptmann said, indicates that the gunman used a semiautomatic pistol with a large-capacity magazine.

Without uttering a word, the assailant walked into the store and up to Kim, who was behind the counter. The businessman was shot five times and was clearly the primary target of the attack, police said. The gunman then began firing randomly at terrified customers and employees inside and outside.

Kim remained in critical condition at UC Irvine Medical Center, hooked up to a respirator. The conditions of Edward Kim and Han Vo, also being treated at the hospital, were upgraded to fair Tuesday afternoon, doctors said.

Police Tuesday identified the customer killed inside the store as Mario Taborga, 21, of Anaheim, who was shot once in the back.

Also killed was Tung Xuan “Tony” Ngo, 18, of Fountain Valley. He and Vo were eating lunch in a Honda in Robotek’s parking lot when the shooting began. When the gunman walked out the front door, he fired at least four bullets through the Honda’s windshield.

The other victim, a 15-year-old boy from Santa Ana, was treated at Garden Grove Hospital and Medical Center and released Monday night. He was shot in the ankle while visiting Robotek, police said.

Detectives have interviewed more than 20 eyewitnesses, including the owner’s wife and four others who were in the store when the killing began, and are piecing together a composite sketch of the gunman. Police described the killer as an Asian in his late teens or early 20s, wearing a dark baseball cap, a dark blue shirt and dark pants. He fled in a 1990 to 1994 gray Mazda MPV minivan parked around the corner.

“This is a coldblooded suspect who is armed and very dangerous,” Sgt. Mike Handfield said.

A man wearing a white tank top also fled the scene after the shooting, outrunning a Robotek employee chasing him, Handfield said. Police are trying to determine if that man was involved in the rampage.

Robotek customers and nearby store owners said Charlie Kim often argued with people at his store.

“He did have a short temper. Maybe if someone raised their voice, he could have just turned away, but he was not that type,” said Kevin Lee, owner of Kevin’s Auto Center across the street. “He would argue back and curse.”

Hassan Mourad, 19, of Huntington Beach described himself as a regular customer at Robotek and said that for the most part Kim acted like a father to the young men with souped-up cars who hung out there. But he added that Kim “didn’t have a lot of patience for ignorant people.”

Handfield said few details are known about the most promising lead, the irate phone call.

Times staff writers Scott Gold, Thoa Hua and Maria Elena Fernandez contributed to this story.