The inevitable has happened! According to People, late last night, Britney Spears was placed in a 72-hour mental evaluation lockdown, after locking herself in her L.A. home with one of her children, and refusing to give the kid back to Kevin Federline. (Though not the right way of going about it, one can hardly blame her.) Even worse? After talking her out, the police strapped her to a gurney!

A source tells PEOPLE it was the pop star’s court-appointed child monitor who called police. “She had already put Preston in the car when Britney locked herself in a room with Jayden,” says the source. “The cops came and got through the door and tied her down to a gurney.”

Spears, who according to police appeared to be “under the influence of an unknown substance,” was rushed to Cedars-Sinai Medical Center, where the source says she will be on a minimum of a 72-hour lock down for mental evaluation.

Life & Style is reporting that the hospital blood tests have come back negative for drugs and alcohol. Meanwhile, another source tells Us Magazine about the crazy scene outside the house…

“They had to strap her down like a mental patient and she was going between laughing and hysterics,” the source adds, calling it “a total psychotic breakdown. She just went crazy.”

A hospital source tells Usmagazine.com that Spears has been designated a “special needs” patient, meaning “they have either overdosed or tried to commit suicide. So we go stay with these patients and monitor them constantly. We watch them so they don’t hurt themselves and watch the people who come visit them to make sure they don’t pass anything to them.”

Currently, Britney remains under observation, and we’ll supply more updates later. Until then, all together now… “EEEEEEEK!”