This week had promised to be no more eventful than others in the quiet life of Helen and Robert Slatkin, a retired couple living in a small town in New Jersey. But to their shock, they find themselves wrestling with the grief of losing their eldest daughter, 38-year-old Gail Ornstein, a jogger slain in Rock Creek Park last weekend.

The parents buried her on Tuesday in New Jersey, and now lie awake trying to figure out what happened.

"Somebody's taken away half of our life," Helen Slatkin said in a telephone interview. "We've had a hundred people over since this has happened and nobody gives us words of comfort because everyone knows there are none for this . . . insanity."

Helen Slatkin described her daughter as "conscientious to an extreme," a "self-motivated perfectionist," who had been living in Washington for about five years.

"She was the absolute strength of our life," her mother said. "She had a mind like a steel trap. We always said that she handled her life very competently. We never had to worry about her. She took care of herself financially. No worries with her. No worries at all except someone killed her."

Ornstein, a divorcee who Helen Slatkin said was dedicated to her work and keeping fit, was found strangled, beaten and sexually assaulted by the side of a popular running trail near the Connecticut Avenue bridge.

An autopsy this week determined that she was attacked sometime between 4 a.m. and 7 a.m., Saturday. Her body was discovered about 2 p.m. that day by a passerby. She was wearing running clothes. Police said yesterday that they have no suspects in the slaying.

Clarke Hutchinson, a close friend of Ornstein, said that Ornstein jogged in the park every morning just after sunrise and was careful not to go out while it was still dark.

"She always talked to me about being careful, [saying] 'Don't do this, don't do that,'" Hutchinson said. "She carried Mace for a while, but she stopped because she never ran into anyone and holding it as she ran was awkward."

"This is all hindsight," said Helen Slatkin from her Leonia, N.J. home, "but we're beating our breasts and tearing our hair out: If, if she had only waited 20 minutes longer, if, if, if."

Ornstein, who had degrees from Oberlin College in Ohio and Pennsylvania State University, lived in a condominium near Rock Creek Park, at 2410 20th St. NW. She worked as a budget analyst for DeLeuw, Cather and Co., an engineering firm.

"I thought she was perfectly safe, as safe as anyone could be today," said Helen Slatkin, who along with her husband is the retired owner of a small trucking firm. "But now people are telling me Washington is a zoo. I live near New York. It's a zoo there. The whole world is a zoo. Why doesn't someone do something about it?"

Ornstein's death has caused concern in other quarters, particularly among those who use Rock Creek Park.

"Obviously, we're all shocked," said Christopher Klose, president of the Woodley Park Citizens Association. "People are afraid. A lot of the neighbors run and they use the park a lot, and I'm sure they're apprehensive."

Police officials said this week that in spite of Ornstein's slaying, they believe security in the heavily used, 1,800-acre park is adequate to protect the public.

"I honestly think crime [in Rock Creek Park] is sporadic," said Capt. Robert Langston of the U.S. Park Police, which is responsible for patrolling the area. He said crime is generally higher at other popular federal parks in the city, such as the Mall, or East and West Potomac parks.

Langston said that Rock Creek Park trails are regularly patrolled by police on motor scooters, in cruisers and on horseback, and by undercover officers on bicycles.

Washington police said that the last D.C. homicide in Rock Creek Park occurred in June 1981, when the body of 21-year-old Catherine Theresa Schilling was found by a trail under the Whitehurst Freeway.

Schilling, a Georgetown University student and para-legal aide at a Washington law firm, was raped, shot and killed apparently while using the park as a shortcut to her home in Georgetown, police said.

The man accused of Schilling's slaying, Donald E. Gates, a 30-year-old laborer, went on trial yesterday in D.C. Superior Court.

In opening arguments, assistant U.S. Attorney J. Brooks Harrington told the jury that Gates had admitted assaulting another woman in the same location 19 days earlier and had told a police informant that he had killed Schilling, who was shot five times in the head.

Gates' lawyer, Hamilton P. Fox III, argued that the first assault, which he said was an attempt to snatch a woman's purse, was the only reason Gates was arrested in Schilling's murder. Fox called Schilling's death a "terrible crime" but argued that the government had arrested the wrong man.

Also contributing to this story was Washington Post staff writer Al Kamen. graphics /photo: Gail Ornstein found slain Saturday.