Forest preserve officials said Officer Patrick Connor resigned late Wednesday. A spokesman said the investigation into the incident continues and aspects of it will be further addressed, but offered no further information or details.
Connor was seen on cellphone video taken by Mia Irizarry, who was celebrating her 27th birthday. She posted the video to Facebook.
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In the video, Irizarry is approached by a man, identified by authorities as 62-year-old Timothy Trybus, who tells her she should not be wearing the Puerto Rican flag shirt in the U.S., and asks, "Are you a citizen? Are you a United States citizen?"
Irizarry is heard telling Trybus that Puerto Rico is part of the United States as he approaches her multiple times.
Irizarry can be heard asking the park police officer, now identified as Connor, for help, and telling him she is uncomfortable. Connor is seen walking away.
As Trybus continues to harass her, other officers arrive and a female police officer finally steps in on behalf of Irizarry.
Trybus is charged with assault, and police said those charges could be updated and could include a hate crime.