Marcia Libes Simon has yet to talk with her children about Tuesday's shooting at a Jewish community center in Los Angeles, and unless her 9-year-old son says something first, she won't.

"If he asks about it, I'll say those things are random," Simon said as she arrived to pick up her children from the Jewish Community Center of Greater Washington in Rockville.

Simon was one of dozens of parents with children enrolled at the Rockville JCC whose thoughts turned to their own youngsters when they learned of the attack, which wounded five people, including three children.

"I was just thinking it could have been one of my kids," the Potomac woman said. "It's just so random and frightening."

The shooting at the North Valley Jewish Community Center in the Granada Hills section of Los Angeles evoked a swift response from the national Jewish Community Centers Association, which ordered its 275 centers to tighten security.

In a statement, the national association advised local centers in the United States and Canada to call on law enforcement agencies to take "appropriate precautions."

Orange cones blocked the driveway at the Rockville center yesterday, the largest in the area. They were moved only to admit unmarked buses that carried youths to day trips or back home. Officials had closed two other entrances and were funneling all members and 850 participants in a summer youth camp through a single set of doors at the front of the building. Montgomery County and Rockville City police patrolled the expansive campus throughout the day.

Capt. Bryan McManus, of the Montgomery County police department's Rockville District, said he dispatched several officers to the Montrose Road center shortly after learning of the Los Angeles shooting. "It's not something we can do all the time," he said, citing staffing concerns, "but in a tragic case like this, I've got the resources."

By mid-morning, scores of concerned parents had already met with Arnie Sohinki, the Rockville center's executive director, to discuss security. Sohinki recalled one frantic mother, who, after dropping off her two preteen sons at camp yesterday morning, told him she was nervous. "We're all a little bit nervous," he told her. Camp counselors were briefed on security and on how to handle questions from youths.

"When you're responsible for kids, you're dealing with the most precious thing to parents," Sohinki said.

Meanwhile, in the District, officials at the Jewish Community Center in Northwest said that the shooting had prompted them to more closely monitor activity around their headquarters but that exhaustive efforts to secure the building were made two years ago when the structure was renovated.

A special electronic card is required to enter through the main doors on Q Street, and parents can't gain access to the preschool without punching in a security code, said Nancy Raskin, the center's executive director.

The executive director at the Jewish Community Center of Northern Virginia was busy yesterday answering calls from concerned parents. The official, who asked that his name not be used because of safety concerns, said that the facility follows a "standard procedure in an event like this" to increase security measures.

But he declined to say what they were, adding that "I don't want to publicize what we do."

Despite the blocked driveway and police patrols outside, all seemed normal inside the Rockville center. A preteen boy rocked to the 1970s disco tune "Burn, Baby Burn" at an impromptu talent show. Groups of senior citizens played bridge in another room.

"Why is there so much security around here?" asked a 10-year-old boy, wearing swim trunks and sandals, as he and a friend walked from the outdoor pool.

"Didn't you hear about the shooting in California?" his 11-year-old friend snapped back. "They're here because they don't want it to happen here."

Staff writer Peter Pae contributed to this report.