Pricilla Garcia was always tagging along with her severely autistic 11-year-old brother.

When Joshua Garcia played computer games, so did she. When he watched cartoons, so did she. And when he hopped into the family's backyard pool in Richmond Hill Saturday afternoon, so did she.

He hopped back out.

She couldn't.

Pricilla's grandmother, Julia Garcia, found the 6-year-old face down in the pool about 20 minutes later. Pricilla died at New York Weill[ Cornell Center in Manhattan early Sunday.

Her father, Victor Garcia, 29, said he watched from behind a window as doctors struggled to revive his child.

"When all eight or 10 of them looked at the clock," he said, "I knew she was gone."

An autopsy Monday morning will determine the exact cause of death, a spokeswoman for the chief medical examiner's office said.

The Garcia house on 117th Street was a scene of mourning Sunday.

Garcia stood dazed in the front yard. One after another, neighbors and friends came to offer their condolences. Even more offered them by phone. A half-dozen relatives sat on the porch steps, staring vacantly at the street.

A new wooden fence blocked the path to the backyard. Behind it, the above-ground swimming pool sat empty. Muck and grime caked its blue siding.

"I'm basically in a state of shock," Garcia said, his voice drained after 12 hours of waiting to see whether his daughter would live. "I'm all cried out."

Leaning back on his red truck, Garcia described his daughter's death as a freak accident that could have been avoided. It began with the silence.

For the past four years, Garcia, a fledgling real estate investor, has lived with his mother and two children on the bottom floor of a two-story house. Saturday, his mother was taking care of both kids. At 3:15 p.m., the children were playing in the living room as Julia Garcia, 58, prepared lunch.

"When she finally finishes the meal, she notices no one is around," he said. "She sees the window open."

The children had climbed out.

Julia Garcia, in a panic, ran out the front door instead of the checking the pool. She called 911. She called her son. She called a cousin in Brentwood.

"Her first reaction was to run up the street this way," said the cousin, Randy Rodriguez, 30, as he pointed to Jamaica Avenue. "She didn't see them. So she ran the other way."

It wasn't until 20 minutes later that Julia Garcia remembered the pool.

She found Pricilla and pulled her from the bottom of the pool. A firetruck arrived moments later.

Meanwhile, Victor Garcia, who was having an alarm installed in his truck a few blocks away, ran back home after getting his mother's frantic phone call.

"When I got here, I saw the firetrucks," he said. "I knew it had to be Pricilla, because she's only 3 feet tall. She can't swim."

Police found Joshua's clothes in the swimming pool, but he was gone. He turned up naked on Atlantic Avenue later in the afternoon, after streaking out of the pool. Police picked him up.

Yesterday, he was cheerfully playing video games in his living room. His family tried to explain the tragedy. He didn't understand.

"He's oblivious to it," Rodriguez said. "He knows she's not around. But he can't comprehend it."