A police cruiser marked the spot yesterday where tragedy struck a Philadelphia police officer's family.

The entire block of Girard Avenue between 57th and 58th streets in West Philadelphia was still as police tried to piece together what led to the death of Joshua Wright, 16, Tuesday night.

Preliminary investigation indicated the mother's service gun went off accidentally during a struggle with her son, according to police.

Police said the mother, whom sources identified as Angela Hall, an 18-year veteran of the police force - now assigned to the 12th District, with headquarters at 65th Street and Woodland Avenue, Southwest Philadelphia - came home from work shortly after 9 p.m.

A neighbor who asked that she not be named said she heard gunfire and looked out of her second-floor window but couldn't see anything. So she went downstairs and peered warily out her front door.

"All I could smell was the gunpowder," she said.

As she stood watch, she said, she saw an ambulance and police swarm the area.

"Then they brought him out," she said.

Chief Inspector William Colarulo, of Internal Affairs, said Hall removed her police-issued gun from her holster and "placed it in another location inside [an enclosed] porch."

Police said that after Hall came home, she and her son began arguing. Wright reached for her gun, he and his mom struggled for it, and then it accidentally went off, fatally wounding him in the head, police said.

"It appears right now that this was an accident during a family dispute that led to a physical altercation over a gun," said police spokesman Capt. Benjamin Naish.

Wright was taken to the Hospital of the University of Pennsylvania, where he was pronounced dead about 10 p.m.

"This is a family tragedy," Naish said.

He said that Hall also was injured in the scuffle and that she will be on leave from the department.

No charges have been filed. However, Naish said Internal Affairs and Homicide are still investigating.

Other neighbors peered out of their houses yesterday, glancing down the block to the house where Wright lived with his mother.

"There were never problems at that house," said another neighbor who asked that her name not be used. "It's terrible." *

Staff writers Simone Weichselbaum and David Gambacorta contributed to this report.