A former D.C. police officer was arraigned yesterday on a charge of second-degree murder while armed in the shooting death of his 74-year-old mother, Margaret Mary Lee, following what police believe to have been a domestic argument.

Police arrested Joseph P. Ellis, 59, of 3310 18th St. SE, Tuesday night when, answering a disturbance call, they found Lee dead; she had been shot in the head. Ellis was arraigned yesterday beforeD.C. Superior Court Judge Henry H. Kennedy Jr., who set bond at $5,000.

Police said they had not yet determined a motive for the shooting. They said they received a call saying there was a disturbance at the 18th Street address at 6:25 p.m., an hour before Lee was declared dead.

Police said it appeared Ellis and Lee had both been living in the apartment. Neighbors of Ellis said they had not known him well before the shooting and they said they had rarely seen his mother in the building.

Ellis was forced to resign from the D.C. police force in 1960 after he was arrested and charged with assault with intent to kill, prosecutors said in court yesterday.

Ellis was later convicted of a reduced charge of assault with a dangerous weapon and given a one-year suspended sentence with two years' probation. Prosecutors did not describe the incident that led to the conviction.

For the last five years Ellis had worked as a sanitation foreman with the D.C. Environmental Services Department, police said