President Obama was briefed by Brennan and the White House is seized of the matter, US officials said.
Meanwhile, various groups have condemned the shooting calling it a "cold-blooded massacre of innocent worshipers".
Indian Minorities Advocacy Network and Muslim Peace Coalition USA condemned the heinous attack and urged the Muslims to hold special prayer services in this holy month of Ramadan for the victims.
Shaik Ubaid, a founding member of ImanNet, urged mosques and temples to ask for extra police protection and to put security measures in place.
"The campaign of hatemongering against the religious minorities and immigrants that is being supported by some mainstream politicians has endangered all Americans," he said.
The gurudwara in Oak Creek has a congregation of 250 to 400, according to its website.
"I just want to say this temple was built a number of years ago and there have never been any problems with this temple," Oak Creek civic body member Dan Jakubczyk said. "They've been a plus to this city and to my district."
