CYANIDE TRIGGERS NATIONAL MAIL ALERT.

Byline: Sherry Joe Crosby and Eric Moses Daily News Staff Writers

Postal officials nationwide were searching Monday for cyanide-filled letters they believe a transient cancer patient may have mailed in her plot to kill medical professionals, police officers and others she disliked.

One alleged target was a West Covina police officer who had arrested Kathryn Louise Schoonover last year on suspicion of erratic behavior. Another was a retired Santa Barbara officer who had responded to a 1994 hit-and-run collision involving Schoonover.

``We don't know the exact motive, but we know that brochures are being mailed to members of the medical profession, and we know she had cancer,'' said Los Angeles County sheriff's Deputy Boris Nikolos. Her actions indicate ``possible revenge, possibly to send out a message,'' he said.

Schoonover, 50, whose last permanent residence was in Carpinteria, was arrested Sunday outside a Marina del Rey post office before she could mail about 100 envelopes, each containing brochures for health and diet supplements and a teaspoon of the deadly poison, enough to be lethal, authorities said.

A postal customer became suspicious of the woman after seeing her stuffing the powdery poison into white business envelopes.

Schoonover, scheduled to be arraigned on attempted-murder charges, is being held without bail at the Twin Towers jail in downtown Los Angeles.

In the past two months, four people in New York state received similar-appearing packets, but authorities did not know whether the powdery substance in those envelopes was poisonous, Nikolos said.

Schoonover has denied mailing the brochures, he said.

``We have not been able to determine if they were sent by Mrs. Schoonover, or if they are related to her, or if they contained any injurious substance,'' said U.S. Postal Inspector Pamela Prince.

Deputies said Schoonover claimed to be a chemist and has shown a working knowledge of chemicals and compounds. She also has experience in education and possibly in the theater, said sheriff's Deputy John Vernon.

Schoonover allegedly targeted medical professionals ranging from phlebotomists to physicians. Computer-generated mailing labels found in the van, in which authorities believe she lived, also listed police officers and a City Council member in West Covina.

Postal inspectors and sheriff's investigators were trying to reach the people whose names appear on the labels.

Lumpy envelope alert

Postal employees were looking for white or gray, letter-size envelopes without return addresses that might feel lumpy.

No envelopes fitting that description had been found in Los Angeles by Monday evening.

``It is not known at this time that any sodium cyanide packages were actually mailed, but we want anyone to be on the outlook for any mailing that might exist,'' Prince said.

She said postal inspectors also are looking for men and women with whom the suspect has been in contact, especially those in medical and law enforcement occupations.

Schoonover was detained by West Covina officers in January 1997 after police said they received a call about her being in the parking lot of a Best Western Hotel. Schoonover was incoherent and unable to answer their questions, police said. They said they found an open gasoline can emitting noxious fumes in the van, and they took Schoonover to a mental health facility for a 72-hour psychiatric examination.

``She wasn't acting quite right,'' said Detective Pete Mena. ``Based on observation and her actions, they felt she could be a danger to herself or to others.''

After her release, Schoonover filed a claim against the West Covina Police Department, alleging that five officers beat and raped her and kidnapped a baby named Lucky. A spokesperson for the City Clerk's Office said the claim was denied.

Schoonover also spoke before the West Covina City Council, claiming police confiscated 22 items from her van, including a baby, ice-skating boots, videotapes and textbooks.

Hit-run leads to targets

Sheriff's deputies contacted Carole Isenberg, a West Los Angeles resident who was the target of a small-claims lawsuit that Schoonover filed in September 1995, on Monday. Isenberg said she had not received any suspicious mailings.

``She hit my car in Santa Barbara,'' said Isenberg, who refused to discuss the claim. ``It was a hit-and-run, so I never actually had any face-to-face contact with her. I never saw her.''

Sheriff's detectives also called the Santa Barbara police officer who responded to Isenberg's report of a hit-and-run collision and told him that Schoonover had an envelope addressed to him.

``I can't imagine that she would have a grudge against me because I didn't have enough evidence against her,'' said Michael Bastanchury, the now-retired motor officer who impounded Schoonover's car. On the other hand, he said, she might have been angry at him for not believing her and for impounding the car.

Experts said sodium cyanide is relatively easy to obtain. Distributors in California are required only to ascertain how customers will use the chemical.

``I've been very surprised at the lack of controls. I don't think there's any law restricting sales of sodium cyanide,'' said Kim Henson, environmental compliance manager for Great Western Chemical Co. of Portland, Ore.

Henson said many chemical companies began to self-regulate the sale of sodium cyanide after the 1982 case in which it was placed in capsules of Extra-Strength Tylenol, killing seven people in the Chicago area.

State and federal regulations are stricter about chemicals that can be used to manufacture illicit drugs such as methamphetamines, Henson said.

Sodium cyanide is commonly used in extracting gold and silver from ores, in electroplating and in insecticides.

Daily News Staff Writer Peter Hartlaub and San Gabriel Valley Tribune Staff Writer Dan Lee contributed to this story.

CAPTION(S):

Photo, box

PHOTO (color) Kathryn Louise Schoonover is scheduled to be arraigned on attempted-murder charges after being arrested with envelopes containing cyanide.

Box: Postal employee or customers who encounter suspicious packages are urged to minimize handling and contact the Postal Inspection Service at [phone].