A crossing guard was assaulted outside an elementary school in Darby Borough during dismissal as students looked on.

The incident happened outside Walnut Street Elementary School on Monday shortly after 3:30 p.m.

Authorities say the guard was helping students cross the street when a man exited his car, chased her down the sidewalk and punched her in the face.

"It's disgusting," said Darby Borough Police Chief Joe Gabe. "She stated an unknown male exited a Nissan Altima and came at her in an aggressive manner, chased her down the street, about a quarter of the way down the block, grabbed her, and struck her in the face with his left fist."

Surveillance video captured the assault. It shows the guard falling to the ground after being hit. She told police that she was knocked unconscious as the man ran back to his car and drove off.

The chief said it's believed the suspect may have been angry about waiting in traffic.

"He may have been upset with having to wait for her to cross children off of the school bus there," said Gabe.

Police said the man was yelling profanities as he drove through the intersection ahead of the attack.

"When he was approaching her, he was yelling more obscenities at her before he grabbed her and struck her in the face," Gabe said.

The crossing guard suffered swelling to her face. Police said she regained consciousness, walked home and then called authorities.

She did not report to work on Tuesday. A male crossing guard filled in at the location.

"We just spoke to her, she's feeling OK, but she's very shaken up over what happened yesterday and is worried to go back to her position as a crossing guard," Gabe added.

Dionne Galloway, a school district employee, said the crossing guard is a familiar and valued presence at the school.

"I see her every day. She's a part of this family, this school district. She crosses these children every day. She's always on time. She's always helpful. I just hope she recovers and is safe," Galloway said. "Her children go to this school, so can you imagine? They shouldn't have to witness anything like that."

Police are asking for the public's help in identifying the suspect, who was seen driving a gold Nissan Altima. They said the car did not have a license plate but had a paper tag in the window.

"It's terrible that a person would come up, just out of nowhere, just maybe frustrated with traffic or having to wait, and goes over and assaults this woman. A male goes over and assaults this woman in front of children," Gabe said, "and has no problem doing it."

"We are tracking you down and we're hoping that we will be able to find you and have you prosecuted. So the best thing to do is to turn yourself in," added Gabe.

Anyone with information is urged to contact police.