A prosecutor said a 24-year-old man killed his father in his bed with a 12-pound dumbbell at his parents’ home in University City at the La Jolla Crossroads apartment complex on Oct. 7. Wearing jail blue clothing, Nikola Chivatchev pleaded not guilty to the murder of his father, Alexander Chivatchev, 64, at his Oct. 9 arraignment in San Diego Superior Court. Judge David Szumowski set bail at $1 million. Deputy District Attorney Mike McCann said the father was killed in his bed after being struck several times in the head with a weight device around 1:30 a.m. on Oct. 7. His mother was also in the apartment but apparently not injured. McCann told the judge the son had made threats in the past to kill others but did not go into detail. McCann said no other charges involving others have been filed. He said the threats to kill others were random and not specific but declined to comment further. “The investigation is still ongoing,” McCann told reporters afterward. Nikola Chivatchev was born in Bulgaria but graduated from high school in San Diego, said the prosecutor. He had attended Mesa College. His parents’ apartment is near La Jolla Village Drive. His attorney, Allen Cazares, said he had no criminal record other than a drunk driving charge in the past. A preliminary hearing was set for Oct. 26, and Chivatchev remains in the George Bailey Detention Facility.