に偶然会った

ran into

→ に
phrase Rare #39,012
ran into Used when you unexpectedly meet someone by chance. The person met is marked with に.
JA: 駅で高校時代の友達に偶然会った。
EN: I ran into an old high school friend at the station.

私は彼に偶然会った

I ran into him by chance.

彼は駅で彼の英語の先生に偶然会った

He ran into his English teacher at the station.

ナンシーは昨日旧友の一人に偶然会った

Nancy ran into one of her old friends yesterday.

先週パーティーでメアリーに偶然会った

I ran into Mary at a party last week.