SAN JOSE — The young woman called 911 and said she was going to kill her family with an Uzi if the cops didn’t show up.

When they arrived, the 19-year-old woman emerged from her home with what looked like a weapon in each hand. Officers yelled at her to drop what she was holding.

She released something from one hand but continued approaching them, still holding a larger item.

As she drew closer, Officer Wakana Okuma fired and the woman crumpled to the ground.

That’s how police and witnesses described the dramatic scene Thursday morning that ended with the fatal shooting of a mentally ill woman in front of her duplex on busy Blossom Hill Road, two blocks east of Oakridge Mall in South San Jose.

Police later discovered that the woman had been holding a power drill, which was painted painted black and measured about 13 inches long on one end and 12 inches on the other, they said in a news release.

But there are still many unanswered questions about the city’s second officer-involved shooting of the year, including who the woman was and why she threatened her family.

But police said the 911 call required a quick and strong response.

“We had a call, somebody with an Uzi threatening to kill family members,” San Jose police spokesman Officer Albert Morales said. “It was a very serious situation, a very dangerous situation for our officers.”

Police did say that the officer who fired the fatal shot is a 13-year veteran of the department and has crisis intervention training.

The woman made the violent threat to emergency dispatchers around 10:30 a.m.

Multiple witnesses described the encounter — captured on cell phone video and posted on the Internet — in similar fashion to this newspaper. About five officers responded to the call. The woman dropped one of the items she was holding onto a front lawn.

But she held onto the second item and kept walking in a slow and deliberate manner, intermittently pausing to point the item at the officers.

When she got within about 15 feet of Okuma the officer fired once, hitting the woman in the chest, witnesses said.

“They told her many times to stop, to drop her weapon,” one witness said, asking not to be named out of privacy and safety concerns. “And she didn’t.”

The wounded woman was rushed to the hospital and died about two hours later.

Only one officer opened fire, Morales said. All of the officers present for the shooting were taken to police headquarters where they were expected to be interviewed about the encounter. The homicide unit is investigating, which is protocol in officer-involved shootings.

Witnesses also said no one else was in the home when the woman made her threat. Beyond confirming that the item in question was a drill, police did not comment further on the case Thursday.

Two people told this newspaper officers removed images or video from their cell phones after they recorded video of the shooting scene. Police denied they tampered with any cell phones.

Family members told police the woman suffered from bipolar disorder and may have not been taking her prescribed medication leading up to the deadly confrontation.

The San Jose Police Department’s previous officer-involved shooting occurred four days into the New Year when an officer shot a knife-wielding man in a Berryessa neighborhood home. The man survived.

Mercury News staff writer Mark Gomez contributed to this report. Contact Robert Salonga at 408-920-5002. Follow him at Twitter.com/robertsalonga.