So the sentence should be:
We saw a boy dashing across the road and getting run over by a car.
No. Did you read posts 4 and 5?
Yes. But I would like to make sure I understood the replies. Am I missing something? Thanks.
Posts #4 & #5 are telling you to use the simple form for your verbs; "dash" and "get".
You keep returning to the continuous form of these verbs; "dashing", "getting".
"We saw a boy dashing..." feels wrong. "We were watching a boy dashing..." works much better. Then you write your sentence this way:
"We were watching a boy dashing across the road when suddenly he got run over by a car".
Even now, I would question why we want to use the continuous verb "watching". The sentence is grammatically correct, but usually we would use the simple form, and say:
"We saw a boy dash across the road, then get hit by a car",
OR,
"We saw a boy try to dash across the road, but halfway across he was run over by a car".
You could also drop the "We saw...", and say, "As a boy was dashing across the road, he got run over by a car", but it needs that change in structure.
There is no need for the continuous form here the way you want to construct the sentence. It's okay, but it makes the sentence awkward. Here is how you might naturally, and usefully, employ the continuous in a followup sentence, and keep your "We saw...":
"We saw a boy try to dash across the road, but he got run over part way across. As he was
getting run over, I had the bizarre hope that, at any moment, the car would transform into an Autobot and step harmlessly over him."
I used "getting" for consistency, but I'd prefer to say "being".
The difference is that, in the second sentence, I
need to use the continuous "getting" (which means I want you to think about the process, or I want you thinking about this as a period of time, not as a momentary event), because I need to speak about something that happened
while the boy was being run over.
Does this make sense?