Tory Lanez Alleged Prison Attacker Is Inmate Serving Life Sentence For Murder

The guy who allegedly attacked and stabbed Tory Lanez in prison is serving a life sentence for a murder charge ... and this wasn't his first violent incident behind bars.

The California Department of Corrections and Rehabilitation tells TMZ ... Tory was allegedly attacked by fellow inmate Santino Casio around 7:20 AM on Monday morning in a housing unit at California Correctional Institution (CCI) in Tehachapi.

We're told prison staff immediately responded, called 911 and started giving Tory medical aid before transporting him to a hospital for further treatment.

Tory's camp says he was stabbed 14 times and suffered collapsed lungs.

CDCR says 42-year-old Casio has been placed in restricted housing pending an investigation.

We're told Casio was sentenced to life with the possibility of parole for second-degree murder, first-degree attempted murder, personal use of a dangerous or deadly weapon, and inflicting great bodily injury.

While incarcerated, CDCR says Casio was sentenced to six years for assaulting a prisoner with a deadly weapon or force likely to cause great bodily injury.

We're told he was also sentenced to two years for possession/manufacture of a deadly weapon by a prisoner.