You can access it on the County Council website.
An online book of condolence is being opened by Offaly County Council for Detective Garda Colm Horkan.
You can access the book on offaly.ie, will all messages to be printed and fowarded to his family.
His remains will be brought to his family home in Mayo this evening, while preparations for a state funeral are under way.
A man remains in custody in connection with the murder of the 49-year-old in Castlerea, Co Roscommon, on Wednesday.
Cathaoirleach of Offaly County Council Cllr. John Carroll has opened an online Book of Condolence available at https://t.co/WAnGaiOd2V to allow the people of Offaly to express their sympathies to the family of Detective Garda Colm Horkan
— offalycoco (@offalycoco) June 19, 2020
Ar dheis Dé go raibh a anam. pic.twitter.com/jlprE6fZuO