“You don’t know how many people are out there,” Ms. Carpenter said. “There’s violent banging on the front door. We have a man alone in his home.”

But a Wayne County assistant prosecutor, Danielle Hagaman-Clark, said it was “ridiculous” to think that Mr. Wafer was deeply afraid but still decided to open the door and fire his gun instead of first calling the police.

“He shoved that shotgun in her face and pulled the trigger,” Ms. Hagaman-Clark said.

Mr. Wafer, 54, called 911 around 4:30 a.m. and said he had shot someone who was “banging on” the door. More than three hours earlier, Ms. McBride, 19, had crashed her car into a parked car in a residential neighborhood about a half-mile away in Detroit.

A witness said that Ms. McBride was bleeding and holding her head, but that she walked away from the scene before an ambulance arrived. It is still unclear, at least publicly, what she did between the time of the crash and her arrival on Mr. Wafer’s porch.

An autopsy found that Ms. McBride had a blood-alcohol level of about 0.22 percent, more than twice the legal limit for driving. She had also been smoking marijuana.