The owner and two employes of a Washington are private security firm have been indicted by a federal grand jury here on charges of allowing a convicted rapist to carry a gun while he worked as one of their security guards.

Named in the indictment returned Friday in federal court were Charles R. Quillin, a former D.C. police officer who was identified as the owner of Metropolitan Protective Services Inc., a Springfield firm; his brother, Robert W. Quillin, and another employe, Craig Whittington.

The indictment also charged the three men with lying to a grand jury investigating allegations that the employe was allowed to carry a gun despite his previous criminal conviction. Investigators said the probe into the Quillin firm is continuing.

Quillin said the allegations against him and his firm were "totally false," and said he was unaware of the employe's criminal record. He said the guard, Michael Carey, had been processed through the special officers branch of the D.C. Police Department on two occasions and that agency had failed to come across his record.

Quillin's firm employs 55 people, and provides security at construction sites, at least one or two banks, retail stores, and apartments, according to Quillin and others familiar with the investigation. The exact locations of Carey's assignments with the firm could nto be determined late yesterday.

Quillin said the indictment was a "mistake" and that the problem concerning Carey amounted to a "lack of information and communication between the police and my agency." He said the criminal charge came out of what he called harassment of his business by the federal prosecutor assigned to the case.

According to the charges filed Friday and to investigators who worked on the case, the investigation began last fall when the U.S. Park Police stopped Carey on a routine traffic charge and discovered through a computer check that he was on parole.

Carey was convicted in July 1973 on a charge of armed rape, according to the indictment returned yesterday against the other three men. The details of Carey's original arrest were not available late yesterday.

Convicted felons are not allowed to carry guns of any kind. According to the charges filled yesterday. Quillin aided and abetted Carey, who allegedly carried a pistol after conviction on several occasions, by allowing him to carry a .357 magnum pistol and a .38 caliber pistol to security jobs in the Washington area.

Carey worked for Quillin's firm between January 1977 and October 1977 according to the indictment. After Carey was stopped on the traffic charge and found to be carrying a gun, the case was assigned to the career criminal unit of the U.S. attorney's office because of Carey's previous conviction.

During the investigation, the Quillin brothers and Whittington were called as witnesses before the grand jury investigating Carey's access to a gun.

Charles Quillin was charged with lying to the grand jury when he said he had seen Carey, carrying a gun in connection with his work. Quillin was also charged with lying when he told the grand jury that he would not have allowed Carey to carry a gun in Washington.

Robert Quillin was charged with lying to the grand jury when he was asked similar questions, as was Whittington.

The Quillins also were charged themselves with carrying pistols without licenses.

Quillin was a D.C. police officer between 1969 and 1974, when he resigned from the force.