No worries Springs, if that's the context of the story and the character, i.e. not modern age and rather formal, then ignore what I said about pov. If that's how the character would think of his mum, then go for it.
What I'm getting at with "he looked behind" is that, while we can suss out the meaning, on first reading it appears grammatically incorrect.
"To look behind" is a prepositional phrasal verb which requires a prepositional object.
For example, "She takes after her mother," after is the preposition which introduces the prepositional phrase "after her mother". It would be grammatically incorrect to say "she takes after," because the reader is forced to ask, who does she take after? So too with "he looked behind." Behind what?
But here you're using behind as an adverb to mean back or backwards. The reader's first reaction to looked behind would be to ask: behind what? For clarity you should likely change "behind" to back or backwards or around.
This is really helpful, thankyou.