godan verb (-ru)
happen to come; come by chance
Describes arriving or passing by a place coincidentally, often when something else is happening. The verb is intransitive and implies an unplanned appearance.
散歩していたら、ちょうど彼が来掛かった。
While I was taking a walk, he happened to come by.
事故の現場に救急車が来
An ambulance happened to come upon the scene of the accident.