The woman, who declined to be named, added that they tailed the BMW in their own car, calling the police to report its whereabouts.
"We could see that they were in a hurry, but they couldn't drive fast [due to congestion]," she explained. "We didn't think too much at the time. We just wanted to follow the car as much as possible.
"Of course, we had to obey traffic rules and not stick too close to the BMW."
The car chase lasted five minutes, after which the family lost sight of the BMW as it got back onto the PIE.
"My heart was pounding, and I had to calm myself down afterwards," she said,
She added that her husband prioritised the safety of his family as she and their daughter were in the car and thus did not act rashly.
The woman is assisting with investigations and hopes the footage she took of the incident can help reconstruct the timeline of the accident.