The shot was fired in the middle of the night, but it didn't wake anyone up. Did you find it strange that the ‘’residents‘’ of the other bedrooms, Anthony and Jean-Jacques, didn't hear anything? And where was Barbara that night, that she didn't notice Henry's death?
You know that your uncle had a fight with his best friend (Jean-Jacques) - it doesn't add up to the fact that Henry's former friend was staying at the mansion the night of the murder.
A few hours ago, your mother said a strange thing: ‘I killed Henry!’. Why does she feel guilty, since she couldn't have done it... or could she?