He didn't want the silencer to be associated with the massacre. It suggests a silent execution attempt.
He took it off to burn Neville's back. Which is a calculated move which a 'crazy' Sheila would not do. Leaving the silencer in the kitchen highlights more Neville's burnt back and the calculated move more.
He realised the rifle with the silencer attached was too long for Sheila.
He knew Sheila had no experience with rifles. If the silencer was left out, people would ask whether Sheila could put it on and take it off.
Putting the silencer away almost out of sight would only take a few minutes to do.
He was not expecting the police to look for a silencer. They didn't.
He was not expecting the relatives to look for the silencer.
He did not consider the silencer to be a piece of evidence. As was not aware of back splatter and did not notice the aga paint.
The rifle came with a silencer. So would be suspicious if there was no silencer inside WHF.
He wanted to leave as little crime scene evidence as possible. So put the silencer away.
He's not going to put the silencer back onto the rifle after burning Neville's back. Forensic tests may show the burn marks were caused by the rifle nozzle. So why would Sheila put the silencer back on ?
He's not going to put the silencer back on the rifle after burning Neville's back. It's quicker to put it away.
Disposing of the silencer would have to be straight away in case he became an immediate suspect. Disposal options would be limited and it may be found if a search was carried out.
Unlike the rifle and bible. The silencer was useful for the execution, however of no use in a framing attempt. So he put away after having to take it off.
