VACAVILLE, Calif. -- A Northern California boy faced attempted murder and sexual assault charges Monday after police say he raped a 13-year-old girl and attacked her baby brother.

Police said the young victims were home alone at the time of the break-in Sunday morning in Vacaville, Calif.

The 14-year-old suspect allegedly raped and stabbed the girl more than 30 times.

The 18-month-old infant awoke during the attack, prompting the boy to also stab him more than 10 times, police said.

The suspect is an acquaintance of the victims' older brother, said Mark Mazzaferro, a Vacaville city spokesman.

Sgt. Denise Quatman told the Vacaville Reporter newspaper that the girl showed "great courage" by somehow getting the suspect to fall asleep, allowing her an opportunity to grab her brother and escape to a neighbor's house and call 911.

The girl and her brother remain hospitalized in critical condition, but are expected to survive.

Quatman said a SWAT team found the male teen asleep in the victims' home and arrested him without incident. He was being held in the Solano County Juvenile Hall on suspicion of two counts of attempted murder and sexual assault.

Mazzaferro said police do not have a motive for the attacks as they were determining whether the teen entered by force or through an unlocked door.

The teen's mother told KCRA-TV in Sacramento, Calif., on Monday that her son is innocent.

The woman, whose name was not released, said she believes her son is being framed by three other teens he snuck off with on Sunday morning.