Gunman was motivated by hate: Romney

"The tragedy in Wisconsin, where the Sikh temple was invaded by a gunman who was motivated by hate, racial hate, religious hate that makes it even more tragic, and tragic too to have a people that are known for their peaceability and their loving nature to be so brutally attacked," Romney said at a campaign event in Des Moines, Iowa.

"We're thinking of them. Our hearts go out to them and to their community across the nation," said the Republican presidential candidate.

Meanwhile, heart-broken at the incident, top American Senators extended their sympathies to those who were wounded and to the families and friends of those who were killed.

"The Sikh religion is known around the world for its foundational beliefs in peace and tolerance, so it is especially disturbing to me that this violence occurred at a Gurdwara," Senator Mark Warner, Co-Chair of the Senate India Caucus told PTI.

"The violent attack in Wisconsin was heartbreaking, and I extend my sympathies to those who were wounded and to the families and friends of those who were killed," said Warner, the Democratic Senator from Virginia.

Deeply saddened to hear of the tragic shooting at the Sikh Temple of Wisconsin, Senator John Cornyn, another Co-Chair to the Senate India Caucus, said: "The victims were, by all accounts, individuals whose contributions to their community and nation positively affected the lives of many people."

"As we reflect on this senseless act, we are at the same time reminded that our nation is built upon a foundation that guarantees the right of all individuals to the free exercise of religion according to their conscience."

"As we look to the days ahead, please know that my thoughts and prayers will remain with the families of the six victims killed, with those wounded, and with the entire Sikh American community, during this difficult time," Cornyn said