When do kids start learning to lie?

My son will be 4 in May and he’s just begun to start lying within the last 6 months. I don’t know how he learned it or when exactly but lately it’s been causing issue. Him and his sister will be playing and she will say ow and run to us crying. She’s exactly 2 years younger than him but she’s not one to lie. She talks really well and in sentences so I ask if her brother hurt her and she will say yeah and tell me what he did and I go to him and he will lie about it. I know this is hearsay bc who can really believe what two toddlers say when you haven’t witnessed it yourself. Another example is today I walk out of the room from putting his sister asleep and I hear him in his room trying to hide something and I pop in and I ask what he’s doing and he says nothing mama. I know he’s guilty bc he used to do this when I’d just catch him doing something bad and he’d say nothing mama when I didn’t even fuss or pick up on him doing anything bad. So after he said this, I knew he did something I’d be upset about. He took these magnets off the fridge by using a stool. Usually I wouldn’t care but these are small and kept high for that fact. I don’t want our youngest to put them in her mouth and choke. He grabbed them and hid them and I only know because he made a paper fall off the fridge and I noticed the magnets were gone when trying to hang it back up. So he’s got them hidden somewhere in our house and I ask where are they and he knew where they were this entire time but chose to lie. I kept repeating he wouldn’t be in trouble I just need them because they’re dangerous to have laying around. He didn’t want to say still. I make him sit in his room alone for 5 mins and I come back and keep asking. I had to literally explain that he wouldn’t be in trouble I just want them back. He finally tells me after 20 mins of the whole ordeal. Is this even normal for a kid his age?