Undated (AP) _ Here is a list of some of the worst recent massacres in the United States. All occurred within one day or the space of a few days. Serial killings that occurred over a long period of time are not included.

- July 18, 1984: Twenty-one people were fatally shot in a McDonald's restaurant in San Ysidro, Calif., by James Oliver Huberty, an out-of-work security guard. Huberty himself was then killed by a police sharpshooter.

- Aug. 1, 1966: Sixteen people were killed in Austin, Texas, by Charles Whitman; most were hit by sniper fire after he climbed to the top of a campus tower at the University of Texas. Whitman was killed by police.

- December 1987: Sixteen people, including 14 members of one family, are killed. The mass slaying is discovered after R. Gene Simmons Sr. is arrested Dec. 28 in the killings of two people in Russellville, Ark. A search of his home near Dover uncovers the remains of 14 family members, who authorities say were killed by Simmons just before Christmas. Simmons was convicted of capital murder on two charges May 12, 1988, and sentenced to death.

- Aug. 20, 1986: Fourteen people were shot to death at a post office in Edmond, Okla., by Pat Sherrill, 44, a postal worker who authorities said was about to be fired. After police sharpshooters arrived, Sherrill killed himself.

- Feb. 19, 1983: Thirteen people were fatally shot in the head during a robbery at a gambling club in Seattle's Chinatown section. Willie Mak and Benjamin Ng were convicted of murder.

- Sept. 5, 1949: Thirteen people were fatally shot in 12 minutes in Camden, N.J. Howard Unruh, who told police, ''I'd have killed a thousand if I'd had enough bullets,'' was found insane and committed to a mental institution.

- Sept. 25, 1982: Twelve people, including five children, were killed in Wilkes-Barre and Jenkins Township, Pa. George Banks, 43, was convicted on 12 counts of murder and sentenced to death.

- Easter Sunday (March 30), 1975: Eleven people, including eight children, were killed at a family gathering in Hamilton, Ohio. A relative, James Ruppert, was convicted of two killings and found innocent by reason of insanity in nine others.

- Palm Sunday (April 15), 1984: Ten people, including eight children, were killed in a New York City apartment. Christopher Thomas was convicted of first-degree manslaughter, the judge citing ''extreme emotional disturbance.''

- July 14, 1966: Eight student nurses were stabbed or strangled in a Chicago dormitory. Richard Speck, 24, was convicted of murder.

- Sept. 14, 1989: Joseph T. Wesbecker, a 47-year-old pressman on disability for mental illness, fatally shoots eight people and wounds 12 others at a printing plant in Louisville, Ky., before taking his own life.

- June 18, 1990: James Edward Pough, 42, walks into a General Motors Acceptance Corp. office in Jacksonville, Fla., opens fire, killing eight and commits suicide.

- Aug. 20, 1982: school teacher Carl Brown walked into a Miami machine shop armed with a shotgun and killed eight shop employees and wounded three others over a $20 welding job. Brown was then fatally shot by witnesses while riding away in his bicycle.

- Feb. 15, 1988: Seven people are killed and five others are wounded at ESL Corp., a defense contractor in California's ''Silicon Valley.'' A former employee, Richard Wade Farley, 39, is arrested. He had been fired for harassing a woman who was among the injured. Charges are pending.

- April 14, 1989: A rampage in Sonoma County, Calif., leaves seven people dead. Ramon Salcido, a former winery worker, is accused of killing his wife, his two daughters, his mother-in-law, her two daughters and a co-worker, and attempting to kill three other people. Charges are pending.

- Jan. 17, 1989: Patrick Purdy, a 24-year-old drifter, opens fire on a Stockton, Calif., schoolyard with a semiautomatic assault rifle and other weapons. Five children and killed and 30 other people are wounded. Purdy then committed suicide.