(CNN) An Illinois park is investigating after a woman accused one of its police officers of standing by as a man harassed her for wearing a shirt with the Puerto Rican flag, saying it was un-American.

Mia Irizarry says she was trying to celebrate her 24th birthday in the Forest Preserves of Cook County last month when the man approached her asking her why she was wearing the sleeveless Puerto Rico flag shirt, which also had "Puerto Rico" written below the neckline.

Irizarry recorded the encounter on her phone, saying she felt threatened, and posted the video to Facebook.

On Monday, Forest Preserves of Cook County tweeted that it was aware of the June 14 incident and video.

‏"After the incident, we immediately launched an investigation pursuant to our personnel policies into the response of our officer," it said, in a series of posts on Twitter.

The officer resigned Wednesday, the forest agency said. The investigation into the incident continues, the agency said.

Timothy G. Trybus, the reportedly intoxicated individual involved in the incident, was arrested and charged with assault and disorderly conduct, according to a police report.

He is scheduled for his first court appearance August 1, the Cook County Circuit Court said.

He will be represented by a public defender, but one has not been assigned to him yet, the public defender's office said.

CNN has attempted to reach Trybus for comment.

"All people are welcome in the Forest Preserves of Cook County and no one should feel unsafe while visiting our preserves," the agency said.

On Tuesday, park spokeswoman Stacina Stagner said investigators will interview the officer this week about the incident. She said the investigation would wrap up soon, but did not elaborate on a timeline.

On Wednesday, Cook County Commissioner Jesús "Chuy" García called for elevated hate crime charges against Trybus.

"A charge for simple assault or disorderly conduct is not sufficient," García said. "We cannot allow that ugly rhetoric to be the norm in Cook County."

CNN has called the state attorney's office for comment on possible consideration of hate crime charges.

García said Forest Preserves should speed up its investigation and discipline the officer involved, "up to and including termination."

'Officer, I feel uncomfortable'

In the footage, a man can be seen approaching Irizarry saying: "You should not be wearing that in the United States of America." He gets closer to her and asks "Are you a citizen? Are you a United States citizen?"

Irizarry can be heard saying that Puerto Rico is part of the United States and the man approaches her multiple times.

Irizarry asks a park police officer to help, saying, "I am renting this area and he's harassing me about the shirt that I'm wearing."

Later she says: "Officer, I feel entirely uncomfortable, can you remove ... please officer" as the officer is seen walking away from her.

Then she says: "Officer, I'm renting, I paid for a permit for this area. I do not feel comfortable with him here, is there anything you can do?"

The officer can then be seen talking to the man who gesticulates back and tells him to "shut the f*** up."

Female officer steps in

More police arrive and Irizarry says she still doesn't feel safe. The man resumes his abuse, saying: "You're not American, if you were American you wouldn't wear that. You know that right?"

A female officer asks to see his ID and can be heard telling him that he's intoxicated, to which he replies, "Well that's your judgment." She explains that Irizarry has a permit and she warns him that he could be arrested "for not being compliant."

"You don't come here harassing people," the officer continues. "People have just as much right to be here as you and when you're drunk, you don't belong here."

The female officer then speaks with Irizarry, who gives her version of the incident and the officer explains that they were called to the area after a report that a man was choking a woman.

Eventually the first officer on the scene takes notes of Irizarry's account of the incident and says that he was at the scene due to the separate incident, noting that she was not being attacked though acknowledging she felt threatened.

Irizarry can be heard explaining to the officer that the incident began when they had asked the group the man was in if they could move as they had a permit for the area. She said the group politely complied but her Puerto Rico shirt appeared to act as a trigger to the man.

Puerto Rico Gov. Ricardo Rossello was on CNN's Erin Burnett "OutFront" on Tuesday night discussing the incident. He said he was "shocked, appalled and disgusted" when he watched the video.

"This was an attack of an American citizen on another American citizen," he said. "Puerto Ricans have been part of the United States and we've been fighting wars with other fellow Americans. We are proud US citizens. People need to understand that."

US commonwealth

Puerto Rico is a US commonwealth with its own constitution, rather than a state. Puerto Rican residents have been American citizens since 1917 and have the right to vote in US presidential primaries, but not in presidential elections.

The Trump administration has received criticism for its treatment of Puerto Rico, particularly for its response after Hurricane Maria struck last September.

The official death toll from Maria stands at 64 but a recent Harvard study estimated 4,645 people could have perished.

Calling for statehood, Puerto Rico's representative in the House, Resident Commissioner Jenniffer González-Colón last month said, "Hurricanes Irma and María unmasked the reality of the unequal treatment of the American living in Puerto Rico."