TOULOUSE, France >> French President Nicolas Sarkozy says authorities are raising the terrorism alert to its highest level across a swath of southern France where a gunman opened fire on a Jewish school before fleeing.

Sarkozy said Monday’s attack in Toulouse, which killed three children and a rabbi, was the worst-ever school shooting in France. One of the weapons used Monday was the same used to kill three paratroopers in two different attacks in the Toulouse region last week.

Sarkozy suggested one person was behind all three attacks.

He said the terror alert level is being raised to scarlet, the highest on a four-point scale, in the region that includes Toulouse and neighboring areas.

Sarkozy said 14 riot police units "will secure the region as long as this criminal" hasn’t been caught.

One witness described the suspect as a man chasing small children and "looking to kill."

One of the guns he used also been fired in two other deadly motorcycle attacks in the area, officials said.

Authorities immediately increased security at schools and synagogues around the country. The attack revolted France, where school shootings and deadly attacks on Jews are extremely rare, and drew strong condemnation from Israel and the United States.

It was the third motorcycle-based slaying in the area in a week.

France, which has seen a low drumroll of anti-Semitic incidents, is particularly sensitive toward the Jewish community because of its World War II past of abetting Nazi occupiers in deporting Jewish citizens.

French prosecutors were studying possible terrorist links but the motive for all three attacks was unclear. Still, issues about religious minorities and race have emerged prominently in France’s current presidential campaign.

News that the gun was used in attacks last week around Toulouse fueled suspicions that a serial killer was targeting French minorities, and not only Jews. The dead and injured in the earlier motorcycle attacks were paratroopers of North African and Caribbean origin.

In all three cases, the attacker came on a motorcycle, apparently alone, and then sped away.

A 30-year-old rabbi and his 3-year-old and 6-year-old sons were killed just before classes started at the Ozar Hatorah school, a junior high and high school in a quiet residential neighborhood, Toulouse Prosecutor Michel Valet said.

Another child, the 8-year-old daughter of the school principal, was also killed, school officials said. Valet said a 17-year-old boy was also seriously wounded.

"He shot at everything he had in front of him, children and adults," Valet said. "The children were chased inside the school."

Nicole Yardeni, a local Jewish official who saw security video of the attack from the single camera near the school gate, described the shooter as "determined, athletic and well-toned." She said he wore a helmet with the visor down.

"You see a man park his motorcycle, start to shoot, enter the school grounds and chase children to catch one and shoot a bullet into her head." Yardeni said in an interview. "It’s unbearable to watch and you can’t watch anymore after that. He was looking to kill."

A police official said the same powerful .45-caliber handgun used in Monday’s attack on a school in Toulouse was used in shootings four days ago that killed two paratroopers and seriously injured another in nearby Montauban, and in an attack that killed a paratrooper eight days ago in Toulouse.

In Monday’s attack, which took place about 8 a.m., the killer also used a .35-caliber gun, the police official said. At least 15 shots were fired at the school in a residential neighborhood in Toulouse, the official said. The official, based in Paris, was not authorized to speak publicly.

A police union official in Paris said to handle a .45-caliber handgun plus a second gun, the shooter knew what he was doing.

"The shooter is someone used to holding arms," Nicolas Comte of the SGP FO police union. "He knows what he’s doing, like an ex-military guy."

All the dead had duel French-Israeli citizenship and are to be buried in Israel, the Israeli Foreign Ministry said.

French President Nicolas Sarkozy rushed to Toulouse to visit the school with Richard Prasquier, the president of CRIF, the umbrella group representing Jewish organizations.

"This is a day of national tragedy because children were killed in cold blood," Sarkozy said, denouncing "the savagery" of the attack and vowing to track down the killer or killers.

"Barbarity, savagery, cruelty cannot win. Hate cannot win," Sarkozy said. "We will find him."

Sarkozy’s challengers for the presidential vote in April and May also hurried to the scene.

The slain rabbi was Jonathan Sandler, who taught Yiddish at the school, according to another teacher, Uriel Torjmane. He reportedly arrived from Jerusalem last September with his wife and children.

France has the largest Jewish community in Western Europe, estimated at about 500,000, as well as its largest Muslim population, about 5 million.

Toulouse, a southwestern city north of the Pyrenees mountains, has about 10,000 to 15,000 Jews in its overall population of 440,000, said Jean-Paul Amoyelle, the president of the Ozar Hatorah school network in France. He said its Jewish community is well integrated into the city.

The school targeted Monday, behind a high white wall with few external markings, was cordoned off by police, who then escorted other children out as forensics police combed the scene. Six bullet holes circled an aluminum fence that surrounds the school.

One officer held a distraught girl, her face in her hands. A mother and son wearing a yarmulke walked away from the site, their faces visibly pained.

"Everything leads one to believe that these were racist and anti-Semitic acts," Toulouse Mayor Pierre Cohen said on BFM-TV.

"This is a Jewish school, well identified as such, and it is normal to think that anti-Semitism is at cause," CRIF, the Jewish organization, said in a statement.

Interior Ministry spokesman Pierre-Henry Brandet told The Associated Press the suspect made his getaway on a dark-colored scooter — just as the assailant or assailants did in the two deadly shootings last week.

On March 10, a gunman on a motorbike shot and killed a paratrooper in Toulouse. Last Thursday, a gunman on a motorbike opened fire on three uniformed paratroopers at a bank machine in Montauban, about 50 kilometers (30 miles) from Toulouse, killing two and critically wounding the other.

One man who lives near the school said he had just spoken with the rabbi before he was killed.

"I said "Bonjour" to him like normal," said the 29-year-old, asking to be identified only by his first name, Baroukh. "Then he went out into the school entrance. I heard the shots and I turned around and saw him on the ground. He looked dead. But I didn’t have much time to see who did it because I panicked and started running away."

Paris police said Monday they are also investigating threats against two synagogues in Paris from last week. A police official said there was no apparent link between those threats and Monday’s shooting.

In Jerusalem, Israeli Defense Minister Ehud Barak said "whether it was a terror attack or a hate crime, the loss of life is unacceptable."

The U.S. government said it joined France in condemning this unprovoked and outrageous act of violence in the strongest possible terms."

"Our thoughts and prayers go out to the families and friends of the victims, and we stand with a community in grief," U.S. National Security Council spokesman Tommy Vietor said in a statement.

Special prayers were offered Monday at a Paris synagogue, attended by Sarkozy, and at Notre Dame Cathedral in Paris. A minute of silence in all French schools was to be held Tuesday. A carnival in Toulouse was canceled and vigils were being held in Toulouse and Paris to honor the victims.

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Elaine Ganley and Thomas Adamson and Sarah DiLorenzo in Paris and Amy Teibel in Jerusalem contributed to this report.