When Ben (Joshua Pascoe) paid his fateful visit, Heather (Cheryl Fergison) was leaving a voicemail message on the answer machine of best friend Shirley Carter (Linda Henry).
> 'EastEnders' death aftermath: Full spoilers revealed
Of how Phil tries to cover up the murder to protect his son, McFadden told What's on TV: "He manages to get hold of Shirley's phone and delete the message without her realising.
"He has to because Heather was on the phone when she answered the door to Ben, so the message machine had recorded everything. Hearing it sickens Phil."
"Family is everything to him," McFadden continued. "First he fakes a burglary, then he destroys the evidence. He gets Ben to throw away the murder weapon - the frame he hit Heather with.
"Then he finds Jay and gets both boys to change their clothes. He burns them so there is no trace of blood on either of them. Then he creates an alibi for them.
> 'EastEnders' exit was emotional, says Cheryl Fergison
"This is a story of loyalty and betrayal - his love of Ben is what forces him to be disloyal to the love of his life, Shirley."
McFadden recently lauded Heather's exit storyline as "one of the best" he has "ever been involved in" since joining the Albert Square soap in 1990.
> Read more 'EastEnders' news and spoilers
Watch BBC One's trailer for next week's EastEnders drama below: