I would make the call.. I used to live next door to a family who thought it was appropriate to punish the 3-4 year old son by putting him in a cold shower in a dark bathroom until he could apologise for his actions. he screamed and screamed. She stood outside the house passing the time of day with me and then laughed when I asked why he was screaming.
I called SS anonymously - they never did anything about it at all but I was pleased that I had informed someone.
Good luck!