(CNN) - Los Angeles Police Department officers had gone 13 years without killing a hostage or bystander while confronting armed suspects.
In the last six weeks, though, such shootings -- described by LAPD Chief Michel Moore as "every officer's worst nightmare" -- have happened twice.
Outlining steps to prevent the deaths of other bystanders or hostages, Moore this week released video of officers fatally shooting a man and the woman he was holding with a knife at her throat in Van Nuys on June 16.
"Tragically, this is another case where officers were forced to make split-second decisions based on the actions of a violent individual," Moore told reporters. "This was a tense situation that unfolded very quickly and it's every officer's worst nightmare."
The Van Nuys shooting happened a few weeks before the assistant manager of a Trader Joe's in Los Angeles was shot and killed by an officer's bullet. Melyda Corado was fatally shot as she left Trader Joe's while police exchanged fire with a gunman who later took hostages in the store.
On June 16, officers responded to 911 calls about a man who had stabbed his former girlfriend inside a church in the Van Nuys neighborhood, police said.
During the incident, officers fired 18 shots at suspect Guillermo Perez, 32, who was pressing a serrated knife against the throat of a woman standing outside the church.
The woman, Elizabeth Tollison, who was 49 and homeless, was shot twice and died later at a hospital, police said.
In the video released by LAPD, Perez -- a large kitchen knife in one hand and a metal folding chair in the other -- is seen moving toward officers. He refused numerous demands to drop the weapon.
After a beanbag gun failed to stop the suspect, Perez moved toward Tollison and held the knife against her throat as three officers opened fire, according to the video.
"Was each round appropriate?" Moore asked. "That's the subject of this investigation and I will not comment on that until I have all the facts."
Moore said the department was implementing new training procedures and expanding use of a nonlethal 40 millimeter launcher that fires a large foam baton intended to stop armed suspects.
"I spoke with members of Ms. Tollison's family and expressed our sadness at this horrible situation," Moore said. "Personally, my heart goes out to this victim's family and I also feel for the officers who were involved in this, as their lives will be forever changed."
Moore said LAPD officers have long been trained to aim a "precise head shot" at suspects during hostage situations.
"The life of the hostage is paramount and protecting that individual from the threat of the assailant," he said. "In doing that, the balancing act the officer has is how to protect them by stopping the suspect's actions."
Moore said the average number of shots fired by officers increased last year along with the number of officers involved in those shootings. The number of shootings in which suspects were armed with knives also increased, he said.
Possible suit on the horizon
An attorney for Tollison's family said Wednesday the family intends to file a wrongful death and negligence claim against the LAPD.
"The real tragedy is the Los Angeles Police Department's tactical response to this incident," Brian Dunn, an attorney with the Cochran Law Firm, told reporters in Los Angeles. "Because of a series of training violations, because of actions that fell completely below the standard of their own training protocol, what we had was a death of a completely innocent person that was totally and utterly preventable."
The department does not comment on pending litigation, Mark Lopez, an LAPD spokesman, said Wednesday.
The Los Angeles City Attorney's Office did not return a request for comment.
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