California is changing its standards for when police can kill under a law signed Monday by Gov. Gavin Newsom, as it tries to deter police shootings of young minority men that have roiled the nation.

"Training matters, yes. Accountability matters, certainly. Transparency, indeed. But culture - changing hearts, changing minds, changing our approach with dealing with one another. I am incredibly cognizant of that responsibilty," Newsom said, reminding those in attendance that the signing of the legislation is just the first step.

The legsilation will modernize the state's standards for the use of deadly force by officers, according to the governor's office.

The measure by Democratic Assemblywoman Shirley Weber of San Diego will change California's existing lethal force standards to require that deadly force may only be used when necessary.

“The bill will basically make everyone in California safer. It will not bring back those that we’ve lost. But we hope and pray that it will prevent those from being lost,” Weber said in explaining her efforts to change the culture of policing in Cailfornia.

His office says it will encourage law enforcement to try de-escalation techniques such as verbal persuasion and other crisis intervention methods.

It was spurred by last year's fatal shooting of Stephon Clark, whose death sparked major protests in the state capital and reverberated nationwide.

The measure passed with bipartisan support after major police organizations won concessions.

The new standards will take effect January 1, 2020.

Previously, law enforcement officers were authorized to use deadly force when there was "reasonable fear" they were in danger, meaning if prosecutors or jurors believed officers had a reason to fear for their safety, they could use lethal force.