Why does the patroller attack Dana?

The patroller thought that Dana was Alice's mother.

Suddenly, I was facing a young white man, broad-faced, dark-haired, stocky, and about half-a-foot taller than I was.

“What in hell …?” he sputtered. “You … you’re not the one.” He peered at me as though he wasn’t sure. Apparently, I looked enough like Alice’s mother to confuse him—briefly. “Who are you?” he demanded. “What are you doing here?”

What to do? He held me easily, barely noticing my efforts to pull away. “I live here,” I lied. “What are you doing here?” I thought he’d be more likely to believe me if I sounded indignant.

Instead, he slapped me stunningly with one hand while he held me with the other. He spoke very softly. “You got no manners, nigger, I’ll teach you some!”

I said nothing. My ears still rang from his blow, but I heard him say, “You could be her sister, her twin sister, almost.”