Two friendly fire deaths of NYPD officers in seven months is leading to new training.

"We have to keep understanding what the NYPD can do better, and I think training is always part of the solution," said Mayor de Blasio.

Detective Brian Mulkeen was killed by friendly fire last weekend as he struggled with a gun suspect in the Bronx.

And in February, Detective Brian Simonsen died in a barrage of police bullets responding to a cell phone store robbery in Queens.

In response the NYPD announced that all plainclothes officers in anti-crime units must undergo tactical training in teams using live firearms and video training simulators at the department's training facility Rodman's Neck, in the Bronx.

The goal: To have the officers become more familiar with how their partners might respond in a shooting situation.

The NYPD said it also is creating local tactical training centers where officers can learn on video firearm simulators. The first one recently opened operating in Queens.

"There is nothing friendly about friendly fire. One of the things that I think we need to think about is that these situations never operate in a vacuum," said Keith Ross, an adjunct professor at John Jay College of Criminal Justice.

Keith Ross, a retired police officer who teaches at John Jay College of Criminal Justice spent 10 years at the NYPD's training bureau after patrolling public housing developments in Queens.

"It's this idea of being hands on, being in the moment and figuring out what you’re gonna do. Because, as most police officers, if they make a mistake, and it’s not a tragic mistake they will go back and they’ll rethink, 'what happened, how can I be better?'” said Ross.

"The department is committed to learning every fact and drawing every appropriate lesson so we can get better at what we do, keep officers safe and continue driving down crime,” The NYPD said.

After Detective Simonsen's death in February, the NYPD formed a committee to review policies to improve ways officers respond to critical incidents. That review is still underway.