A 57-year-old man accused of threatening to plant a bomb at a South San Francisco police station has pleaded not guilty in San Mateo County Superior Court to charges of making criminal threats.Gerardo Kelly has been in custody in lieu of $50,000 bail since his arrest in early April. On Tuesday, he pleaded not guilty to charges of making a false bomb report and making criminal threats, according to the San Mateo County District Attorney’s Office.South San Francisco police said Kelly called the Police Department’s front desk about three times between 3 p.m. and 6 p.m. April 6. He “was talking crazy” and accused police of lying, police Sgt. Joni Lee said.Kelly eventually told police he was going to put a bomb in the South San Francisco police station and start killing the officers one by one at midnight, according to the district attorney’s office.He also allegedly gave his name and address to the officers, who rushed to his house and found him lying on his bed. No weapons or bombs were found, according to the district attorney’s office.Kelly is expected to go to trial July 27.