4 Suspects Linked to 4th Murder, Robberies : Crime: Law enforcement officials say the two men and two women may have been involved in several armed assaults in the San Gabriel Valley. They were arrested after three shoppers were abducted and slain.

Four people arrested in the slayings of three San Gabriel Valley shoppers have been tentatively linked to at least one other murder and are suspected in a string of armed robberies, law enforcement sources said Saturday.

Los Angeles County sheriff’s officials and West Covina police say the two men and two women may have been involved in a spate of armed robberies during the last two months in La Puente, Covina and West Covina, in which bandits seized cars and sometimes assaulted their victims.

At least eight such robberies have occurred in the San Gabriel Valley, although sheriff’s officials say they have not yet connected these incidents to the four suspects.

Authorities on Friday arrested the four--two men recently released from jail and two women--in a predawn raid on their West Covina apartment. The break in the case came when hidden cameras at automated teller machines showed the suspects using their victims’ stolen ATM cards to withdraw money.

At least one of the victims was abducted from the Puente Hills shopping mall, and the other two were also killed while on shopping trips.

Investigators have been able to tie the suspects to at least one additional killing in the San Gabriel area, sources said. The sources refused to reveal details of the crime.

Of the four in custody, authorities point to Vincent Hubbard, 26, as the apparent ringleader. Hubbard was described by state parole officials as a veteran gang member whose criminal record goes back nearly 10 years.

Hubbard was released from prison July 15, after serving five months for a cocaine possession charge that violated his parole.

Investigators said Saturday that they believe Hubbard launched a series of robberies almost immediately after his release.

“He got out, and he got very busy, very quickly,” said one detective involved in the case. “They were really, really busy.”

Hubbard was convicted of a series of drug, theft and burglary violations as a youth in the early 1980s, according to Jerry DiMaggio, regional parole administrator. Hubbard first went to state prison in 1985 for possession of marijuana for the purpose of sale and was sent back to prison in 1986 for first-degree burglary.

More recently, he received a 16-month sentence in 1989 for battery on a correctional officer, but was released after nine months, in June, 1990. He was sent back to prison last February.

Arrested with Hubbard was John Lewis, 21, who was released from the California Youth Authority two months ago after serving four years for assault with a deadly weapon and burglary.

They and two women--Robin Machuca, 26, and Eileen Huber, 20--are being held virtually incommunicado in separate cells at the West Covina Jail. Arraignment is scheduled for Tuesday in West Covina.

The bodies of two of the victims, Shirley Denogean, who disappeared after telling co-workers she was going shopping, and Elizabeth Nisbet, abducted from the Puente Hills mall--were found dumped along freeways. The third victim, Willie Newton Sams, who vanished as he walked to a store from his West Covina home, was found in a trash dumpster at a nearby school. All had been shot.

Sgt. Kevin Smith of the sheriff’s station in City of Industry said at least eight robberies have occurred in the last two months in the San Gabriel Valley area in which cars were stolen at gunpoint.

Two took place last Monday, the day before Denogean was killed, Smith said.

In one case, the robber intercepted a motorist early in the morning at a gas station in Valinda. He punched the victim in the face, climbed into his car and forced the victim to drive some distance before ordering the man onto the street.

The robber then told the victim to start running as fast as he could and that if he turned his head he would be shot. The victim ran, and the bandit drove away in the victim’s Volkswagen Beetle.

Later that night at a small shopping mall in City of Industry, a 21-year-old man leaving his car was intercepted by a gunman who demanded his car keys. The victim handed the keys over, and the robber drove away in the victim’s 1991 Toyota Celica.

The robbery occurred a short distance from the Puente Hills mall where Nisbet had been abducted two days before.

Meanwhile, other details emerged Saturday about the suspects, who neighbors said frequently held all-night drug and alcohol parties in Apartment E at a West Covina housing complex.

The younger woman, Huber, who apparently has no criminal record, has told investigators she is pregnant by Lewis. Machuca, who is Lewis’ sister, has a young daughter who was in the apartment at the time of the raid, investigators said.

The girl, believed to be 4 or 5 years old, was turned over to child welfare officials. Neighbors had reported hearing a child cry for several hours one night last week, screaming, “Please don’t leave me mom!”

Times staff writer Jesse Katz contributed to this story.