Police said the devout Sikh died of massive head injuries suffered on his first shift for security company CNE.
The company had been contracted to stop thieves targeting the yard for scrap metal.
Kaur couldn't understand why her son was out patrolling alone on his first night and without a walkie-talkie to contact a support person.
She had many questions for the company but she had not yet heard from them.
"I want to know if the man there has a child. I want to know why my son was there by himself, on his first night working at a place targeted by thieves."
Dhaliwal had only his cellphone as a means of contact.
"He had called his friend at 1.45am and said he was feeling like it was a lonely place," Kaur said. "If he had called me I would have said he shouldn't be there."
CNE Security owner Cherag Noshirelavia would say only that Dhaliwal was an employee of First Security, but had picked up additional work with his company.
Police believe Dhaliwal was attacked between 2am and 2.30am. A workmate found his slumped body in a pool of blood at 3.15am at the construction site.
They are still seeking a group of four Polynesian males, estimated to be aged between 17 and 20 years old, known to have been in the area when Dhaliwal was killed.
Karamjit Kaur has had to postpone this month's trip to New Zealand because her other son was injured after a car door was opened on him when he was cycling.
"He is still recovering," she said. "The doctors are helping him but he can't move yet. They are trying to help him stand."
Her son's death and her other son's accident were further blows to the family, already devastated after Kaur's husband was killed by a drunk driver in 2004.
Anyone with information relating to the death of Charanpreet Dhaliwal could call the investigation team on 0800 OP HOPE (0800 674 673).