A nine-year-old boy remains in hospital in serious condition.
"My vehicle shook, so did the auto next to me, and someone rolled down their window to ask if I was alright", she told CTV News London.
Investigators remained at the scene Monday trying to piece together exactly what led to the deadly crash.
Mayor Ed Holder called the deaths "an unspeakable tragedy".
Martin said there were a few dozen people on the sidewalk, and several drivers got out of their cars to help.
"I can't get the sound of the screams out of my head", Martin said.
Police arrested a 20-year-old man from London a short time after the incident occurred, around 10 minutes away from the scene.
Police Chief Steve Williams said one adult female who was struck died at the scene, while an adult male, adult female, and two children were rushed to hospital by paramedics.
The victims were two women - aged 74 and 44 - a 46-year-old man and a 15-year-old girl. The child was expected to survive.
"The direction of travel hasn't been released at this time", Const. Sandasha Bough said when asked about the vehicle involved in the fatal crash. The family had immigrated from Pakistan 14 years ago and were dedicated, decent and generous members of the London Muslim Mosque, he said. My heart breaks for the family, friends and the entire community. "I just wanted to see".
Police have scheduled a news conference with more details for Monday afternoon. "We really have to deal with islamophobia, it's real".
Qazi Khalil said he saw the family last Thursday when they were out for their nightly walk.
Police also confirmed that the suspect wore a vest similar to body armor during the incident Sunday and that potential terrorism charges are being considered.
The National Council of Canadian Muslims said it was beyond horrified, saying Muslims in Canada have become all too familiar with the violence of Islamophobia. "I can't really come to the terms they were no longer here".
"We understand that this event may cause fear and anxiety in the community and in particular the Muslim community and any community targeted by hate". A single police cruiser was parked outside the Oxford Street mall Monday morning, where yellow police tape cordoned off a small section of the parking lot.
Police said the suspect had not had any contact with London police prior to the incident. Eleven police officers formed a line and slowly walked in unison through the scene, scouring the ground for evidence.
Holder said flags would be lowered for three days.