The Maryland chief medical examiner's office still has not issued a ruling on the cause and manner of the death of an Alexandria man killed in a police chase and shootout on the Capital Beltway last week, leaving open the question of whether the man killed himself, died of injuries sustained in a fiery car crash or was fatally shot by a police officer.

Prince George's County police, who are investigating the death of Merachew Lucas Fitigu, 24, said yesterday that they believe he may have committed suicide by shooting himself in the head after leading Fairfax police on a 10-mile chase on the Beltway on July 27. But they cautioned that they have not ruled out other explanations for his death.

"Preliminarily, we are looking into the possibility that the suspect committed suicide," said Prince George's police spokesman Royce D. Holloway. He said police expect to complete the investigation soon after they receive a final autopsy report from the state medical examiner's office in Baltimore, perhaps within a week.

But authorities have not released any specific information about the final minutes of Fitigu's life, such as whether they believe he shot himself before or after the crash, or what prompted a Fairfax County police officer to shoot at Fitigu as he sat in his burning car.

Prince George's police are investigating the case because Fitigu died in the county after leading Fairfax police on a chase from Virginia across the Woodrow Wilson Bridge. Police said they found a 9mm semiautomatic pistol, 1.75 pounds of marijuana and $1,000 cash in Fitigu's black Pontiac Trans Am after he crashed into a guardrail just north of the Temple Hill Road overpass.

Authorities have refused to say whether the gun found in the car had been fired or whether any shell casings were recovered from the scene of the crash. Police have said they found shell casings on the Virginia side of the Wilson Bridge.

Relatives of Fitigu, the son of an Ethiopian diplomat, said they are upset at the lack of clear answers. "We stand around, but we have no idea what to say or what to think," Fitigu's sister, Yodit Fitigu, 27, said in an interview.

Dressed in traditional black Ethiopian mourning clothes outside her mother's apartment in Fairfax, Yodit Fitigu said the family has not heard from Prince George's investigators since last week, when police indicated that they believed Fitigu had committed suicide.

Fairfax police officials have said their pursuit of Fitigu began when he passed through a radar monitor in the Kingstowne area of the county. He eluded police there, but the pursuit picked up again on the Beltway after officers said they saw Fitigu driving erratically. As Fitigu and three patrol cars following him approached the Wilson Bridge, Fitigu fired shots at the police, piercing the fiberglass shell above the grill of a patrol car driven by Fairfax patrol officer Jeffrey K. Rockenbaugh, police said.

Fairfax police said they did not return fire but continued to chase Fitigu into Maryland, where he apparently lost control and struck a guardrail. Rockenbaugh and two other officers quickly arrived on the crash scene and approached Fitigu's car, which was in flames.

What happened next is still unclear. Police sources said investigators believe Fitigu shot himself once in the head as the officers got close to his car. But they believe Rockenbaugh thought that Fitigu was aiming at his pursuers, prompting the officer to fire once at Fitigu, striking him in the right shoulder.

Sources said this scenario is supported by the account of a witness--a Prince George's Fire Department battalion chief who came upon Fitigu's burning car while on the way to another incident--who reported hearing two shots.

Fitigu was pronounced dead at the scene. Yodit Fitigu said that she can't accept the idea that her brother may have killed himself.

"Suicide? No. I really bet my life that he wouldn't do that," she said. "It just doesn't fit him. He's so shy, he's so timid that he blushes when people ask him a question."

Yodit Fitigu said her brother had been taking computer programming classes and was working at a convenience store and a computer retail shop in Northern Virginia.