LOS ANGELES -- Two men charged with murder in the killing of former “General Hospital” actor Johnny Wactor pleaded not guilty Thursday in a Los Angeles court.

Robert Barceleau and Sergio Estrada, both 18 years old, entered not guilty pleas through their lawyers to charges of murder, grand theft, and attempted robbery.

A third defendant, Frank Olano, 22, facing charges of being an accessory after the fact, also entered a not guilty plea. A fourth, Leonel Gutierrez, charged with grand theft and attempted robbery but not with Wactor's murder, is expected to enter a plea next month.

Requests for comment from the attorneys representing the men were sent to the LA County Public Defender's Office, but no response was received immediately.

Wactor was shot and killed when he interrupted three thieves stealing the catalytic converter from his car on May 25. Police and prosecutors said the 37-year-old had left work at a downtown LA rooftop bar with a coworker when he saw three men who had hoisted his car. One of them fired at him without provocation and killed him, authorities said.

Following a comprehensive investigation, which included police requests for public assistance, the four individuals were apprehended on August 15 and formally charged on August 19.

The charges against Barceleau include special circumstances, such as murder during an attempted robbery and personal use of a firearm, which could result in a life sentence without the possibility of parole if he is convicted. Estrada faces a maximum sentence of life in prison for his charges.