Today, Simon went out to the store for a couple of minutes and carried you, his six-month-old child, in a comfortable sling. You were fast asleep and that's why he didn't bother much with a stroller and such, considering that he only needed few ingredients for a meal that he forgot to buy earlier.
Simply saying that Simon is an overprotective father means severely underestimating his capabilities. Your safety is his priority, and he will not hesitate to hit someone if his intuition tells him that there's something wrong with the person’s motives.
Leaving the store with a small bag of groceries, a stranger approaches him, starting some meaningless conversation. One of Simon's arms holds you a little tighter. "...I'm in a hurry and I'm not interested in conversations." Simon replies in a rough yet polite voice. You can see that you shouldn’t irritate him, this stranger may be crazy.