Six people, including a D.C. policewoman and at least three children, were shot and killed yesterday inside a blood-smeared house in the Camp Springs section of Prince George's County.

One victim, a woman, was found at the foot of a staircase in the brick split-level house at 6700 Coolrdige Rd. Five of the slain were found in the back of the house in a bedroom.

The carnage, the worst mass murder in the Washington area in years, was described by one county police officer as "the worst thing I ever saw in my life."

The slain policewoman was identified as Ingrid M. Ellis, a sergeant assigned to the 2nd Police District in Northwest Washington.Police said they were tying to find her husband, Ron, described as a mechanic, for questioning.

Police said they had no suspect in the shooting and knew of no motive. However, they said evidence did not indicate that the slayings followed a burglary or robbery.

Except for the policewoman, none of the victims was formally identified as of early this morning.

However authorities said the adult victims were Sgt. Ellis and two other women in their thirties. Also killed were a boy about 12 years old, a girl the same age and another girl said to be 4 or 5 years old.

Neighbors said that Sgt. Ellis and her husband had three daughters.

Authorities said the house, about one mile southwest of Andrews Air Force Base, was visited about 3 p.m. yesterday by a real estate agent who was showing it to persons apparently interested in renting or buying it. Investigators said they found indications that the Ellises had packed and were preparing to move.

Police said it was believed that four of the victims were in the house when the real estate agent arrived at 3 p.m. It was not immediately known if the four were residents or visitors.

In addition, police said, a man, who has not been identified, was in the house, talking on the telephone, when the agent arrived.

At 6 p.m. another agent arrived to show the house and found the door ajar, police said.Inside, at the foot of a staircase, the agent found a woman's body.

When the agent emerged from the house, a neighbor said, "her hands were shaking."

Police were summoned and when investigators arrived, they determined that the woman at the foot of the stairs had been shot in the head. Then they went upstairs and found the other bodies. Some were lying on a bed in the back bedroom and some on the floor.

Some had apparently been shot several times, police said. Investigators said there was no sign of any struggle. The room was smeared with blood, they said.

One or more rifles were found in the house, police said, but it was not known if they were used in the shootings.

Authorities combed the house and the area around it for a hours last night and also interviewed neighbors in an attempt to obtain clues and find possible witnesses. Neighbors interviewed by reporters appeared, however, to know little about the Ellis family.

The three Ellis daughters were identified by neighbors as Tracy, 15, Tammy, 13, and Monica, 4. The older daughters were described as students at Walker Mill Junior High School.

Neighbors said they believed the family had lived for two or three years in the quiet residential neighborhood of homes in the $85,000 to $120,000 price range.

Sgt. Ellis, who joined the D.C. police force in 1970, served in the training division until recently when she was promoted to sergeant and assigned to the 2nd district.

The six victims appeared to be the largest number of persons murdered in a single incident in the Washington area in more than eight years.

In early 1973, seven Hanafi Muslims were slain in a house at 7700 16th St. NW. In 1976, four persons were fatally shot in a fast food restaurant in Fairfax County.

On March 1, 1978, according to Montgomery County police, five members of the family of former State Department official William Bradford Bishop Jr., were beaten to death in their home in Bethesda.

The house where yesterday's killings occurred occupies a corner lot at the intersection of Coolidge and Allentown roads.