Prince George's County police said yesterday they are still trying to figure out why Gary Albert Hopkins Jr. allegedly lunged at an officer and tried to grab the policeman's gun at a party last weekend, an episode that cost the 19-year-old college student his life.

Hopkins, who was fatally shot by another officer early Saturday, is the sixth person to die this year after struggling with Prince George's police. If the other cases are any indication, it will likely take authorities several months to make an official determination of how Hopkins died and whether police acted properly.

In two other fatal shootings involving Prince George's police this year, department investigators and county prosecutors spent about five months investigating each case before officers were cleared of wrongdoing.

Authorities took four months, on average, to examine two cases in which an Oxon Hill man and a Clinton man died of heart attacks shortly after they were subdued and arrested by police. No charges were filed in either case, and the officers involved returned to active duty.

One other case is still pending--the Sept. 22 death of a Suitland man who stopped breathing in a holding cell shortly after he was arrested for fighting with officers.

Eugene W. Grant, a Seat Pleasant community activist who serves on an advisory board to Police Chief John S. Farrell, said the public becomes skeptical when such investigations drag on for months, even if the police are exonerated in the end.

"In all these cases involving the police department, it takes too long to investigate," Grant said. "It certainly doesn't take them that long to investigate a charge against a civilian."

All deaths involving police officers in Prince George's are reviewed by a county grand jury, which examines evidence collected by homicide detectives and state medical examiners.

"The grand juries are very deliberate and thorough," said Paula Burr, a spokeswoman for the Prince George's state's attorney's office. ". . . Citizens would rather the grand juries err on the side of taking too long than rushing things."

Lt. Andy Ellis, a spokesman for the county police department, said homicide detectives usually meet with prosecutors from the state's attorney's office within two weeks of a deadly incident to discuss the case.

But Ellis said the investigations often hinge on autopsy results and toxicology tests that can take several weeks to complete.

"What we find is that most of the holdup is getting these presented to the grand jury," Ellis said.

Autopsy results are pending for Hopkins, of the 9700 block of Woodberry Street in Lanham, who was shot by an off-duty police officer about 2:30 a.m. Saturday.

Police said the shooting occurred after a fight broke out at a party at the West Lanham Hills Fire Department. Two off-duty county police officers, who had been hired to provide security, were told by someone in the crowd that three men sitting outside in a car had been involved in the fight and were carrying weapons, Ellis said.

The two officers called for backup, and a third police officer soon arrived. That officer drew his gun, approached the car and told three men inside--including Hopkins--to put up their hands and get out, Ellis said. One passenger ignored the command and ran off, he said.

As the other two men got out of the car, Hopkins lunged at the officer and tried to wrest away his service weapon, Ellis said.

As the officer and Hopkins fought, one of the off-duty officers--identified as Officer Brian C. Catlett--fired one shot into Hopkins's upper chest, Ellis said.

Hopkins was pronounced dead 30 minutes later at Doctors Community Hospital in Lanham. Family members said yesterday that they were still trying to piece together what happened.

"There are a lot of things to be questioned," said Hopkins' aunt, Debbierena Hopkins. "We're going to let the investigation take its course. But we also rest in our faith that the truth will be told and revealed."