بسم الله الرحمن الرحيم
It is severe sin to pass in front of the person who is praying salah. Hadith sternly forbids it, those who do so they are sinner. And passing close to a namazi i.e. in the place of sajdah is severe sin.
If the said person did so intentionally then it is a serious issue, but if it was done by mistake then too he should have sought pardon.
Note:A detailed fatwa on passing in front of the praying person is published in the book “Chand Ahem Asri Masail” vol. II. This book is available at Maktaba Darul Uloom Deoband, you may purchase it and it could also be read online at the website of Darul Uloom Deoband.
Here is the book link:
Allah knows Best!
Darul Uloom Deoband