Two men and a woman were shot and killed in the Aquasco area of southern Prince George's County last night in what police described as a double homicide and suicide. The gunfire touched off a tense five-hour siege that ended when heavily armed police made their way into the trailer home where the shooting occurred.

The killings in the extreme southeastern tip of the county stemmed from what appeared to be a domestic quarrel, according to a police spokeswoman. One man was fatally shot outside the trailer, and the woman and the other man were found inside.

Police provided little information about the relationships among the three, but neighbors living in the largely rural area said they understood the woman and man inside the trailer to be an estranged husband and wife. They said the second man may have been a friend or neighbor of the wife who had accompanied her to the trailer.

That man was found fatally shot about 6 p.m. near the trailer in the 20000 block of Aquasco Road. Gunfire that broke out after his body was discovered prompted calls to police that touched off the long standoff in which police waited, guns drawn, in the rain and mist.

Earlier in the evening, a resident said that an official of a local fire and rescue department began tending to the man who was found outside the trailer, near a hardware and fishing supply store, but was forced to withdraw when gunshots were heard in the vicinity.

The man was eventually taken to the Southern Maryland Hospital in Clinton, where he was pronounced dead on arrival, according to a county fire department spokesman.

Police swarmed the area, closing roads and keeping several residents from homes and chores, according to neighbors. Yellow police tape went up in the area near the trailer home, about 50 yards from Aquasco Road.

Neighbors reported that police tried to contact the occupants of the trailer by telephone. It was not immediately clear whether they were successful.