But when 12-year-old Alexandra came home from school Wednesday afternoon, her sister says she went up stairs, alone.

Ten minutes later, the family found her on her bedroom floor, dead.

The police report says a white karate belt was tied around her neck and the other end tied to the top of the bunk bed frame. But police aren't ruling the death a suicide.

The sister told us the family thinks she was playing "the choking game" -- although police are downplaying that scenario.

"This choking game thing is new to us and possibly new to a lot of students," said Randy Matheson with the Renton School District.

So first thing Thursday morning, students at the McKnight Middle School, where she attended, were told what happened. A dozen grief counselors consoled students.

Three Renton schools received a letter saying the girl may have died as playing "the choking game", and gave a list of its warning signs.

The district decided to tell the students even though her death by playing by "the choking game" has not been confirmed.

"And we want them to know that it's dangerous and they shouldn't engage in that activity," Matheson said. "And moreso we want them to come forward that if they knew of other students who might be engaged in this activity."

So what is the choking game? Here's what some kids are saying in Internet chat rooms about "the choking game":

"It's cool, because when you're out, it like sleeping," said one student in the San Francisco area for a news story there. "Dude, that game is so fun. You actually dream stuff."

Instructions are even posted on the Internet, showing how kids choke themselves or each other for a thrill.

"It's kinda why we go on roller coasters, scary movies -- knowing the end is going to turn out OK," said child psychiatrist Dr. Herbert Schreier. "This is a form of that. And it's a way of choking/ fainting essentially, and then waking up."

But choking is dangerous because cutting off oxygen to the brain could cause brain damage, and even death.

13-year-old Gabriel of northern California died after becoming addicted to the choking game. He died in his bedroom too.

"He's sitting down with his math book on his lap; he had a rope around his neck," said Sam Mordecai, the victim's brother.

"Some kids don't do it by choking. They do it by pressure," Schreier said.

The King County Medical Examiner ruled the cause of death: "death by asphyxiation due to hanging." They did not call it a suicide.

Police are continuing their investigation.

As for how common is the choking game? As best we can determine, it's not common at all but it's growing in popularity because it is a way to get a rush or a quick high without using any drugs.

In fact, Dr. Phil's show on Tuesday -- the day before Alexandra's death -- was devoted to kids getting high and dying doing "space monkey" -- that's another name for the choking game.

The Warning Signs:

Here's what to look for as warning signs for kids that might be playing "the choking game."