screeched to a halt

0Hi, 02br
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00I have an unclear sentence and here it is:02br
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00When the lorry 01u00screeched to a halt02u00 in front of him (he was driving a car) he didn't notice it. In fact, he didn't realise anything was wrong until his car was 01u00halfway underneath02u00 it.02br
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00I don't understand: if the lorry screeched to a halt what means it stopped suddenly then what the second sentence mean? What was the action?02br
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00Thank you.0-