According to witnesses and police, the driver, Saeed Noori, an Australian citizen of Afghan descent who had arrived in Australia as a refugee, deliberately ran a red light then accelerated into an area with a speed limit of 40 kilometres per hour (25 mph), where he ran into the pedestrians.

[4][5] The nineteen injured included nine foreign nationals: three from South Korea, and one each from China, Italy, India, Venezuela, Ireland, and New Zealand.

[7][8] An off-duty officer of the Victorian Police was credited with quickly subduing the suspect,[9] who was wrestled to the ground, handcuffed, and arrested.

[22] In an informal police interview, he "spoke of dreams and voices, but also attributed some of his activities as well due to the mistreatment of Muslims".

"[25] On 22 December, the Victorian Police stated that while they had not yet determined Noori's motivations, "we haven't found anything at all to indicate his linkage or involvement with any type of extremism with any terrorism organisation or anything of a terrorist nature".

[29] Premier of Victoria Daniel Andrews praised the off-duty police officer who responded first, saying he "instinctively came to the aid of others, in the protection of public order, and potentially, avoiding so much other carnage".