A Los Angeles County Sheriff's deputy remains in grave condition and on life support two days after being shot in the head while off-duty inside a Jack in the Box restaurant in Alhambra, CA, the Los Angeles County Sheriff's Department said Wednesday morning.

Deputy Joseph Gilbert Solano, a 13-year veteran with the department, was standing by the restaurant's counter when a man shot him once in the head from behind, authorities said.

A 30-year-old Utah man, Rhett Mckenzie Nelson, was arrested in Long Beach Tuesday on suspicion of attempted murder, KTLA reports. He's suspected to be involved in another shooting in downtown Los Angeles an hour before the Alhambra incident, Los Angeles police Chief Michel Moore said.