DETROIT — A suburban Detroit man who insisted he killed an unarmed woman on his porch in self-defense was convicted of second-degree murder Thursday after the jury rejected his tearful claim that he fired through a screen door in the wee hours because he feared his life was at risk.

No one knows why Renisha McBride ended up at the Dearborn Heights home of Theodore Wafer last Nov. 2, although prosecutors speculated that the 19-year-old woman may have been confused and seeking help, hours after she had crashed her car blocks away. An autopsy found she was extremely drunk.

The jury convicted Wafer of second-degree murder, manslaughter and a gun-related charge after deliberating for about eight hours over two days.

Wayne County Judge Dana Hathaway warned that she would lock people up for any outbursts, and the courtroom was silent after the verdict was read.

McBride’s mother, Monica McBride, cried and clasped her hands as if praying. She gave long hugs to prosecutors as the courtroom emptied.

Wafer, 55, who had been free on bond, was ordered to jail to await his Aug. 25 sentencing, despite vigorous objections from his attorney, Cheryl Carpenter. He faces up to life in prison.