Ideally I prefer to use ‘mown’ and I checked the actual dictionary definition. I think when a cyclist gets crushed under a lorry, ‘mown’ is more appropriate.
I am glad that some journalists do write ‘mown down’ sometimes, but others, probably the right-wing press, still use ‘knocked down’ (which feels more like a light shove) or ‘trapped’ so as not to ‘disturb’ their readers, perhaps with scary words like ‘crushed or mown’.
a. to destroy or kill indiscriminately or in great numbers, as troops in battle.
b. to defeat, overwhelm, or overcome: The team mowed down its first four opponents.
c. to knock down.”
I bet the police say ‘mown’ too.