DETROIT — Crystal Webb cringes whenever a patrol car appears in her rearview mirror.

Her personal experience with police, plus recent shootings of unarmed black men by white officers, has led the mother of two to ask: Who are the good guys and who are bad?

‘‘You are the people I’m supposed to go to when I’m in trouble,’’ Webb, of Apple Valley, Calif., said of police.

Two-thirds of young African-Americans and 4 in 10 Hispanics say that they or someone they know has experienced violence or harassment at the hands of the police, according to a GenForward poll.

But the poll also shows that young people still want a police presence in their communities.

GenForward is a survey of adults age 18 to 30 by the Black Youth Project at the University of Chicago with the Associated Press-NORC Center for Public Affairs Research. The first-of-its-kind poll pays special attention to the voices of young adults of color, highlighting how ethnicity shapes the opinions of a new generation.

Those poll results come after the killing of several young black men by police around the country. Two of the more recent killings were the July 5 shooting death of Alton Sterling during a struggle with officers in Baton Rouge, La., and the fatal shooting of Philando Castile the following day by an officer in a suburb of St. Paul, Minn.

Those shootings were followed by the July 7 killing of five officers in Dallas by a black gunman during a protest. Two officers and one sheriff’s deputy were killed by a black gunman during a July 17 ambush in Baton Rouge.

About 6 in 10 young adults consider the killings of black people by the police and violence against the police as extremely or very serious problems, the poll said. But young African-Americans and Hispanics see killings by police as more serious problems and young whites see violence against the police as more serious.

Webb, who is black, said she was arrested in November by two officers — one white, the other black. ‘‘When I gave them my story, the other officer who was white gave me a look,’’ she said. ‘‘While the officer of color was asking questions and being nice, the other officer got in the car and started yelling at me. He told me to just shut up.’’

The charges eventually were dropped by a judge, she said.