You can clearly see she hit him, and moved him with her vehicle in those four seconds and you can really see that. I'd invite anyone to also take a look from an earlier time leading up to it, and from across the street that is additionally informative. Mind you it's black ice and slippery conditions that the agents are walking upon:
https://www.youtube.com/watch?v=Jbq98aqF794
This is an earlier 48 second clip, that leads up to and includes the one you shared from a different angle.
-One can also observe and understand that with her window rolled down, and her arm hanging out her window, she's been ordered twice verbally to "get out of the car" as was played in audio of the same videoclip of yours on BBC last night, yet this audio is often talked over or edited out by the likes of CNN last night, same video clip.
-Upon hearing the twice given orders, does Renee' have the option to chose to keep her vehicle parked and comply with the detainment order given to her? Does she get out of her car or stay put?
No.
-Instead, sadly, Renee' puts her car in reverse as noted by the backup lights coming on, along with her vehicle subsequently backing up about 4 feet. She is evading detainment at this point.
-Next, as an agent is attempting to put his hand in the car to unlock the door, Renee chose to put her car into Drive and Accelerate.
If she left her vehicle in park, and complied with orders given to her, she'd be alive. Tragic.