The Duchess of Cambridge has sent a private message described as "deeply personal and heartfelt" to the family of murder victim Sarah Everard, The Mirror reported.
She wrote the letter to show support to the family.
Ms Everard's death, after allegedly being abducted while walking home, touched a nerve in Britain and has prompted calls for action to reduce violence against women.
"Kate's letter was deeply personal and heartfelt, she expressed her absolute sadness at what Sarah's family and loved ones are going through," a source told The Mirror.
"She said she knows that no words can change what happened but that she wanted to let them know that they and Sarah are in her thoughts."
"This was a private matter to her and she wanted to show unity with everyone else who shares these feelings."
Kate has previously made a visit to Clapham Common, where a memorial has been set up for Ms Everard.
She said the circumstances of the killing reminded her of times she had returned home late in London before marrying Prince William.
Ms Everard's killing has sparked concern over the violence and harassment women often face.
It has also produced support against a government plan to give police wider powers during protests.
London's Metropolitan Police were criticised as being heavy-handed when trying to end a memorial for Ms Everard, arguing they were also acting on coronavirus lockdown safety orders.
After Ms Everard's death, MPs suggested plainclothes police be put on duty in bars as a way to prevent attacks on women, which was also challenged by women in the country.