A teen-age girl who said she wanted to "liven up the day" opened fire with a .22-cal. rifle on an elementary school from the window of her home today, killing the principal and a custodian before she surrendered, police said.

A policeman and at least eight pupils were woundd -- two critically, police said.

The girl, identified as 16-year-old Brenda Spencer, barricaded herself inside the family's modest home across the street from the Cleveland Elementary School for 6 1/2 hours before she quietly agreed to come out, police said.

A policeman, Sgt. Dave Kelly, said Spencer emerged from the house, put two guns on the ground, then calmly went back in the home and brought out her ammunition before heavily armed officers grabbed her and took her to police headquarters. No charges were immediately filed, but police said possible charges included murder and assault with intent to commit murder.

Reporters for the San Diego Tribune talked to the girl by telephone in the midst of the shooting spree and asked why she did it.

"I just wanted to," she said. "I don't like Mondays. This livens up the day.

"I just started shooting. That's it. I just did it for the fun of it."

Just before hanging up, she said, "I have to go now. I shot a pig [police officer], I think, and I want to shoot some more."

Asked if she was shooting at anyone in particular, the girl answered, "No one in particular. I kind of like the red and blue jackets."

All the shots were fired within 15 minutes starting at 8:40 a.m.

When the shooting began, students ran in panic from the school yard and teachers told others to huddle beneath desks and keep away from windows. Later, students were ushered to safety in the school auditorium. Nearby homes were evacuated.

All those hit by gunfire were outside the school. Police reports indicated that either eight or nine pupils were hit by the shots, and two were listed in critical condition at Alvarado Hospital in San Diego, authorities said. A policeman, Robert Robb, 30, was shot in the neck as he tried to carry a wounded student to safety, they said. Killed were Burton A. Wrage, 53, the principal, and Michael Suchar, 56, the custodian. Both were walking to school when the shooting started.

Spencer was described as a "pretty good shot" by officer on the scene. They quoted her father as saying she had 500 to 600 rounds of ammunition.

During negotiations between police and the girl, police spokesman Bill Robinson had described her as being "under a lot of pressure." He added that he didn't know if the girl had any prior problems with authorities.

One 16-year-old classmate of Spencer's said yesterday that she often talked of shooting people. "She said before she's going to make her living being a sniper." The friend, who declined to give her name, said that Spencer was given a.22 cal. rifle for Christmas. "She's been crazy about guns. She's good shot."

The friend added that she also expressed hatred for police officers. "She hates cops. She's always saying she wants to kill cops, always saying she wants to blow one away. I thought she was crazy. But I thought she was just talking and I didn't think she'd really do it. When we'd be watching cop shows and one got shot she'd say, 'All right.'"

Jennifer Engle, 10, a student at the elementary school, said, "I started walking to school. I saw the principal and he was laying flat on the ground, he wasn't moving or anything. I saw two holes in his leg and then I saw the custodian and he was groaning. Mr. Barnes [another teacher] told me to start running and I started running and heard this shot from a gun. I ran around the corner but I wasn't really scared at first. I thought at first it was a drill or something. But then the teacher blocked the door with a piano, they said on the radio the principal had died and so had the custodian."

Kathy Voeks, 11, said that she was "close friends" with the slain custodian. "I was really scared but I didn't cry, none of us till we got home back to our parents."

She said she walked to school from her house a block away and "I saw Mike [Sjchar, custodian] on the ground and they couldn't get to him, but then the policemen backed upa garbage truck in front of the house so they could take him out of there. Mike was groaning 'Oh God, oh God. Go get the police.'"

Frank Stites, whose 7-year-old daughter, Audrey, was shot in the elbow, said, "She won't say very much about what happened. She is much about what happened. She is kind of in shock. It'w hard to say what is going on in her mind."

Theapproximately 320 students were kept at the school for more than an hour and then taken by bus to another school.

Wrage and Suchar were both rushed to a hospital. Suchar was dead on arrival and Wrage died in surgery.