A paramedic among the first responders to the scene of the mass shooting in San Bernardino on Dec. 2 told the Los Angeles Times he fell back on his training as he moved from victim to victim, determining if each was alive or dead and marking the deceased with white tape so rescuers could focus on the survivors.

He said he his training taught him to make the judgment in five seconds.

"In five seconds, you look at their skin color, their breathing and you feel their pulse," he told the Times. "By all those things, you are determining if they are critical or deceased."

Ryan Starling, 33, said he was actually training with a specialized team of responders, near the scene of the shooting, by coincidence. He said team members switched out their blanks for real bullets in their assault rifles and rushed to the emergency.

Because they were close by and responded so quickly, San Bernardino Fire Capt. Mike Arviso told the Times that as many as five people survived who might have otherwise bled to death.

Read the full account of the responders here.