A Los Osos man accused of killing his mother pleaded not guilty today in San Luis Obispo Superior Court.

Michael Bret Van Heuver, 23, entered his plea to a charge of premeditated murder in connection with the death of his mother, Lisa Van Heuver.

The incident occurred April 27 at a home on Seventh Street near San Luis Avenue, sheriff's officials said. Upon arrival, deputies found Lisa Van Heuver unconscious on the floor after apparently being assaulted.

Sheriff’s spokesman Aaron Nix said Lisa Van Heuver was brain dead and taken off ventilation — in accordance with her family's decision — before her death May 15.

Michael Van Heuver was initially charged with attempted murder in San Luis Obispo Superior Court, entering a plea of not guilty, before the amended charge was brought following his mother’s death.