I'm sure the father has all the trust for the son, but his son knowing the father has the bitcoin stored on his phone was probably tempted to steal it. Nowadays, it's hard to trust anyone even your family, so it's better to keep silent about your holding and make sure you don't store in an online wallet if we are speaking of a huge amount of money already.
What disturbed me more here is the Son willing to kill the father just for the money, not the bitcoin stolen by the son.
After I read the article, I think the son has no intention of killing his father, the son just wants to make his father faint to get his father bitcoins, I think maybe the child has an addiction to drugs so he wants to steal the assets owned by his father, but still whatever the reason for the child to do it, it is clear that what he did was quite bad and should not be imitated.
Storing bitcoins on cell phones is not a good move, but we know that cellphones are now the only thing that we often carry and are the simplest for us to access, so I think that's the reason the old man kept his bitcoins on his cellphone, but to be honest, I don't agree if the father hides Bitcoin assets from his family, let alone his son, because after all, his wife's children have the right to know about the assets that the man has.