Authorities in Hollister have made multiple arrests in a homicide case.   39-year-old mark arballo was found with severe injuries last January on the 3-hundred block hill street.  he later died from his injuries.  2-suspects were arrested thursday, and another 2 were arrested friday.   all 4 of the suspects are juveniles, and were booked into san benuito county juvenile hall.  22 year year old Conrad copado has also been charges in conncetion with the murder.  he was already in state prison for an unrelated offense.