The man who was home with a Red Bluff infant at the time of his death is sitting in the Tehama County Jail.
While he is considered a person of interest in the case, investigators say they do not have any evidence to charge him with the seven-month-old's death.
They are hoping an autopsy will clear up questions about the child’s death.
"Mom came home and found the child unresponsive in the crib," Lt. Dave Greer said.
Red Bluff Police officers and Tehama County Sheriff’s deputies immediately began CPR after receiving the call around 2 p.m. Sunday, but were unsuccessful.
The attention then turned to the man who was supposed to be watching the baby boy.
"I think he is or was in a relationship with the child's mother," Greer said.
Deputies questioned the man, who they are calling a person of interest, but say he couldn't tell them the last time he checked on the boy.
They took him into custody on a parole hold in connection with a previous misdemeanor DUI conviction, but have not released his name.
"Until we prove cause of death I do not want to place any bad press on this individual at this time,” Greer said.
Investigators are treating the infant's death as suspicious because he didn't have any known medical conditions.
While they say there were no obvious signs of trauma they are hoping an autopsy will give them an idea of what happened to the boy.
"That's one of the things the pathologist will look at is any type of trauma to the child. That's the nice thing about a pathologist is he can tell if that is pre death or post death," Greer said.
Deputies are hopeful they will be able to keep their person of interest in custody until they complete the autopsy.