This situation carries serious consequences on multiple levels and the assault of a corrections officer is what transforms a manageable problem into a potentially devastating one.
Cell phone possession in a California state prison is already a significant infraction. Under federal law the Contraband Cell Phone Act carries up to five years of additional prison time, though in practice California state facilities typically handle phone possession through the institutional disciplinary system rather than new federal charges. The standard response is SHU placement ranging from six months to a year followed by a transfer to a higher security facility. For a Level 3 B yard inmate, that transfer could mean moving to a Level 4 facility, a significant step up in restriction and difficulty.
The assault of a corrections officer changes the entire picture. Assaulting a peace officer in a California correctional facility is a serious felony under California Penal Code. New criminal charges can be filed by the district attorney's office regardless of what is happening inside the facility's own disciplinary system. A conviction on assault of a peace officer can add years to the existing sentence, and prosecutors pursue these cases aggressively because officer safety is treated as a priority.
Both inmates involved in the assault face the same exposure. The fact that two people acted together does not reduce individual culpability and in some cases complicates the legal situation further by raising conspiracy considerations.
The immediate consequences include the SHU, a disciplinary hearing, likely new criminal charges, a classification increase, and a transfer to higher security. An attorney needs to be involved immediately to assess the criminal exposure before any hearings take place.