Highland Park’s mother, suspect Robert Cremo, angrily confronts the SWAT team in the wake of the July 4 mass shooting.

Video acquired by CBS News Dennis Pessina is shown screaming and pointing at officers in McDaniels Street, Highland Park, on Monday, while she was on a massive chase for her son.

It is unclear what caused the confrontation, but the network reported that Ms. Pesina was in contact with police for several hours after the shooting at the Independence Day parade.

It also emerged that a Pesina-owned company had a mailbox in a UPS store just a few blocks from the scene of Monday’s shooting.

CBS News reports that police have put the UPS store under seal, and no one has been able to enter it since Monday.

Ms. Pesina yelled to reporters to “get off my property” as she left the family home on Tuesday, the first time she had been seen since Monday.

Ms. Pesina and the suspect’s father, Bob Cremo Sr., retained high-ranking Chicago attorney Steve Greenberg.

On Wednesday, Greenberg said the parents unfairly blamed their son’s acquisition of the high-powered assault rifle used in Monday’s deadly attack.

“The ‘system’ is trying to make this about parenting,” Greenberg said Wednesday.

“The biggest question, which must be answered and answered, is why are military assault weapons available for anyone to buy?”

Greenberg did not immediately respond to a request for comment.