Gunshots cracked the air on a sunny morning as two men led a group of high school teachers on a tour of a violent area of West Oakland. As the teachers fled to safety, the local guides hurried to the chaotic scene on the nearby corner of 13th and Peralta Streets.

A young man named Darius Jenkins lay on the ground bleeding as friends and neighbors panicked. Sam McNeal, an attendance counselor for McClymonds High School, crouched at his side and urged him to keep breathing while Ron Muhammad, a widely known community organizer, ran to the fire station about a block away. There he discovered a truck full of firefighters, waiting in the driveway.

“What’s going on?” Mr. Muhammad asked. “Something’s happened to this guy, and y’all just sitting here.”

Mr. Muhammad said the firefighter replied: “It’s our policy. We have to wait for police.”

Across the country, first responders are often required to wait for law enforcement officers to arrive before entering a violent-crime scene. The policy is intended to keep paramedics and emergency medical technicians safe. But in Oakland, where emergency crews are often faster than the police, the delayed medical help can have tragic consequences, feeding a culture of distrust and anger.