She expressed her concern in a letter addressed to his brother Amarjeet Singh Kaleka for the 'bhog ceremony' (ritual) here today at Gurdwara Singh Sabha.
Gandhi deputed Union Minister and local MP Preneet Kaur to deliver the letter to Amarjeet personally.
In her letter, Sonia said, "I am deeply regretted by the death of your brother Satwant Singh Kaleka in the ominous mishap of the Wisconsin Gurudwara in Oak Creek. I am really shaken by his untimely demise. I offer my hearty condolences on the 'bhog' organized in his remembrance."
She condemned the attack and noted, "An attack like this on any religious site is really shameful."
"I, once again, want to offer my condolences to those martyrs who died during this genocide and pray to God to bless their families with the courage to bear their sorrow," she said.
Gandhi also announced Rs 2 lakh each to the families of those who were killed in the shootout.
