It was a 6 year old boy, also from the MSN article:

He revealed that Wen and his family were in high tension because of several incidents of home disturbances.

The family had allegedly experienced their house doors being “banged at midnight and evening.”

Zou said, “His three kids were terrified and worried that somebody tried to break their door and break in.” He also shared that just the night before the incident, two people had knocked on their door severally and ran away before he opened the door.

Certainly no excuse for pointing a gun but gives at least a little context to his paranoia.