NEW YORK (AP) _ A man was convicted Friday of manslaughter rather than murder in the Palm Sunday 1984 killings of 10 women and children, one of the city's worst mass slayings.

A state Supreme Court jury found that Christopher Thomas had carried out 10 intentional murders, but reduced the conviction to 10 counts of first-degree manslaughter because of ''extreme emotional disturbance.''

''I just couldn't believe it,'' Eddie Lopez, the ex-husband of one victim and father of two others, said of the verdict. ''If I'd been on that jury I would have given him the maximum.''

District Attorney Elizabeth Holtzman said Thomas would spend ''virtually the rest of his life in prison.''

Justice Ronald Aiello set sentencing for Sept. 10 and said, ''It is not unusual for a judge to impose the maximum on anyone who committed a murder this brutal.''

The convictions for first-degree manslaughter, or intending to cause serious physical injury that results in death, carries a maximum sentence of 12 years in prison.

The rejected charge, second-degree murder, which is intentional murder, carries a maximum life imprisonment for each count.

Thomas, 35, was accused of fatally shooting eight children, ages 3 through 14, and two women on April 15, 1984, in Brooklyn's East New York section. An 11-month-old girl was the only survivor.

The jury acquitted Thomas on 10 counts of felony murder - committing a murder during a robbery. It convicted him of two illegal weapons charges.

Aiello had instructed the jurors to consider ''extreme emotional disturbance'' as a mitigating factor on each count.

''I felt it was the best possible thing to do,'' said jury foreman Anthony M. Baglione. ''I felt there was extreme emotional disturbance.''

Defense attorney Martin Schmukler said he was satisfied with the verdict, saying ''there was just too much evidence of bizarre behavior by the defendant.''

The prosecution said Thomas believed his wife was having an affair with convicted drug dealer Enrique Bermudez, who owned the house where the killings took place.

Bermudez's pregnant girlfriend and two daughters were among the victims.

Prosecutor Christopher Ulrich also maintained that Thomas and Bermudez had a falling out over a drug deal.

Convicted armed robber Jeff Ford, imprisoned at Rikers Island with Thomas last year, testified that Thomas told him he went to the Bermudez home the day of the murders to recover $600 paid for cocaine he never received.

Ford said Thomas told him he got into an argument with a woman at the home, that he shot the women, and that an accomplice, identified as ''Lenny,'' shot the children.

The prosecution maintained that Thomas carried out all the killings.

Medical testimony indicated that all the victims were shot in the head at close range and died within minutes of each other.

Police testified that a spent .22-caliber cartridge found at Thomas' Bronx home and spent shells found at the killing scene came from one of two guns used. The other weapon was a .38-caliber revolver, ballistics experts testified.

Other witnesses testified they saw Thomas looking bizarre in or near the Bermudez home during the day of the slayings.

Thomas' wife, Charmaine, testified that her husband was enraged when he found her at the Bermudez home without him and set fire to the couple's home when told she was leaving him.

Earlier, Bermudez said Thomas sought him as a sex partner for his wife, but denied he accepted the offer.

Bermudez also testified that Thomas came to his house early on the morning of the killings seeking drugs and money. He said Thomas promised a surprise when asked about some $9,000 he already owed the drug dealer.