LOWELL — Stephanie McNulty says she had never met the police officer before — but he seemed to think he knew her.

McNulty filed a civil complaint against Officer Daniel Houston alleging harassment on Thursday following their encounter at Shedd Park earlier that day. He is accused of calling her a “little (expletive),” telling her to “shut the (expletive) up” and slapping her phone away when she began to video record him.

“It was unprofessional,” she said. “I’ve never seen a cop act like that in my life.”

Around about 11 a.m., McNulty said she was having a picnic in Shedd Park with her three children — the oldest 7-years-old and the youngest just under 2-years-old — and a caseworker from the Massachusetts Department of Children & Families.

About a half hour into her weekly visit with her children, an officer with the Lowell Police Department approached the group. She said the officer, which she later identified as Houston, accused her of giving him false information. According to McNulty, Houston claimed he new her from an arrest at an area department store.

But McNulty said she had never spoken to the officer before and told him she didn’t know what he was talking about.

From there, she said the encounter continued nearly 45 minutes.

According to McNulty:

The officer asked for her identification, but she said she could not provide it, because she didn’t have identification on her.

The caseworker tried to speak to the officer, but as the situation continued, the caseworker took the children away from the scene. McNulty said she also tried to leave, but was told she was being detained.

Officer Houston called for backup and a second officer arrived.

McNulty called both the Lowell Police Department and state police asking for another officer to come to the scene, but was not helped.

McNulty took out her phone to film the officer, but after a few seconds he slapped her phone out of her hand causing it to fall to the ground and shattering the screen.

“He smashed my phone on the ground,” she said.

Officer Houston later realized McNulty wasn’t the person he thought she was and apologized, she said.

McNulty said she went to the Lowell Police Department and filed a complaint following the encounter.

According to McNulty, she sent the short video she took to her mother, who posted it on social media, where it has circulated.

The video does not show the officer cursing, but does show the phone suddenly dropping after McNulty uses it to film the officer’s name and badge number.

Lowell police Capt. James Hodgdon confirmed Friday internal affairs is conducting an administrative investigation into the incident.

“If true, these are not the actions I expect of our officers,” Lowell Police Superintendent Kelly Richardson said Friday.

The investigation will include interviews with McNulty and any witnesses of the incident to determine if the allegations can be substantiated. McNulty said she is scheduled for an interview with the head of the investigation at the police department on Monday.

She is in the process of acquiring an attorney.

When asked about Houston’s current job status on Saturday night, Hodgdon said there would be no comment during the investigation.

The officer has been a member of the department since 1996.

Staff Writer Aaron Curtis contributed to this report.