Some say prosecutor Collier Vale blamed himself for the slaying of a police informant in a tragic mix-up and believed his career was over at age 39. But no one thought he would kill himself.

Perhaps not even Vale thought that - until the last moment."It appears to have been a spontaneous event," Monterey County's chief deputy coroner, Glen Brown, said of the self-inflicted gunshot.

Authorities are still investigating Vale's apparent suicide Oct. 5 at his apartment. He didn't leave a note. And although colleagues say he seemed to linger with goodbyes the day before he died, he didn't appear suicidal.

"I don't know why this happened," said Vale's boss, District Attorney Mike Bartram.

Friends say Vale felt tremendous guilt when an informant was killed Aug. 8, 1989, after information got out that she was helping police investigate a double killing in Seaside, 115 miles south of San Francisco.

Through a mix-up of similar telephone numbers, Vale called Songia Petite Johnson, 20, instead of Sonjii Yvette Johnson, 23, who was a witness in the July 16 double killing. Both women lived in the same high-crime neighborhood and both their names were pronounced "Sonya."

While trying to interview the wrong woman, Vale said enough for her to figure out that the other woman was an informant.

Authorities speculate that, largely to protect herself from drug dealers, Songia Petite Johnson spread the word that the other woman was the "snitch." Three weeks later, Sonjii Yvette Johnson was shot to death. Officials wouldn't say where Songia Petite Johnson could be located for comment.

After the mix-up was discovered, the Johnson slaying was assigned to the state attorney general's office. Vale was widely blamed in press reports for the young woman's death. The story also was televised nationally on "A Current Affair" about a week before Vale's death.

"When you have so many fingers pointing at you and saying you caused another person's death it's going to have an effect on you," said Monterey Police Sgt. Fred Ragghianti.

Vale claimed he was given incorrect information, and authorities say a police officer may have confused the numbers. Vale's defenders say he offered the informant police protection three times.

Still, Vale's guilt feelings persisted.

"It bothered him considerably, that he might have caused this lady's death," said Superior Court Judge John Phillips, who gave Vale a job in the district attorney's office in 1979.

"When you're a prosecutor or a police officer you're supposed to be hardhearted and not let things get to you," said Sheriff Bud Cook. "I think he felt maybe he did something wrong . . . and it finally got to him."

Bradley Hardison, 25, is charged with killing Sonjii Yvette Johnson to prevent her from testifying in the double killing. Hardison was a friend of Anthony Jacobs, 25, who later pleaded guilty to manslaughter in the earlier slayings.

Johnson reportedly overheard Jacobs talking about the double slayings.

Melinda Young, a court reporter in Salinas who was Vale's girlfriend for several years, said that in the weeks before his death he was consumed with thoughts of the Johnson case.

"He felt so helpless, so terribly vulnerable," she said. "He was miserably unhappy about all this. It was the catalyst for him feeling that his career was, as he put it, `over.' "

Vale was likely to lose his job as a top prosecutor in January when a new district attorney, Dean Flippo, takes over. During his campaign, Flippo often said: "When I run the office no one is going to get killed."

Four years ago, Vale left the prosecutor's office to go into private practice. But he couldn't stay away. He rejoined the office within a year.

"He was always a fighter in court," Ragghianti said. "Once he got a case, he took it all the way. But if a case called for compassion he had compassion, too. I guess he felt too much."