TIFU by scaring an autistic child to tears

I work in retail, we had some issue with theft, so we put barricades in form of a stanchion on two sides of the entrance, so customers are forced to exit only from one direction, which gives us better view into what they're carrying.

Literally today I had a man steal something by putting it in his bag, and he ran out when I tried to stop him, so I was slightly on edge.

Suddenly I saw that someone in a black jacket is bent over the stanchion, and tries to move it. I immediately ran towards that person, and politely, but still very sudden and loud said "GOOD MORNING" to grab their attention. He then literally started shaking, looked at me, and I immediately noticed that it's a (severely) autistic teenager... I know the kid, cause he's been here before, and he is non verbal, and I noticed in that moment that his parents were also in the store.

He ran towards his mother and started crying.

I almost died of embarrassment on the spot, apologized about ten times, and just moved away to not scare him any more...

My colleague almost pissed her pants laughing at my mistake.

TL;dr : I thought someone is trying to move a stanchion to steal from my workplace, but it was just an autistic kid, and my reaction made him cry.