The target was an object on the ground well within the confines of the Warren Grove (search) firing range, a 2,400-acre scrub pine expanse used by the military to train pilots in bombing and strafing.

But when the heavy gun in the left wing of an Air National Guard F-16 fighter jet fired Wednesday night, it sent 25 rounds of 20mm ammunition smashing through the roof and zinging off the asphalt parking lot of the Little Egg Harbor (search) Intermediate School 31/2 miles from the range.

At least eight of the 2-inch-long lead rounds punched their way into classrooms, Police Chief Mark Siino said.

A custodian was the only person in the school at the time, and no one was injured. The school will reopen Monday after damage is repaired, education officials said.

Military investigators are trying to determine how the strike could have happened.

The projectiles, which do not explode, were meant for a ground target 31/2 miles away, said Col. Brian Webster, commander of the 177th Fighter Wing of the New Jersey Air National Guard, which is responsible for the range.

Webster said he did not know why the gun fired.

The single-seat jet was flying at 7,000 feet at the time. It was assigned to the 113th Wing of the District of Columbia Air National Guard, based at Andrews Air Force Base in Maryland and returned there after the shots were fired, a Guard spokesman said.

Military officials would not identify the pilot. Operations were suspended at the firing range pending completion of the investigation.

"The National Guard takes this situation very seriously," said Lt. Col. Roberta Niedt, a spokeswoman for the state Department of Military and Veterans Affairs. "The safety of our people and the surrounding communities are our foremost concern."

Mike Dupuis, president of the township's Board of Education, said school workers are mindful that the firing range is nearby.

"That's always in the back of our minds. It is very scary. I have children in that school and relatives that work there," he said.

The Warren Grove range, about 30 miles north of Atlantic City, has been used by the military since the end of World War II, long before the surrounding area was developed.

In 2002, an Air National Guard F-16 that had been practicing at the range crashed along the Garden State Parkway. The plane's pilot ejected safely, and no one on the ground was hurt.

Errant practice bombs were blamed for forest fires that burned more than 11,000 acres of the Pine Barrens near the range in 1999 and more than 1,600 acres in 2002.