"My thoughts are with the Jewish community and all those affected by the appalling act in Texas. We condemn this act of terrorism and anti-Semitism," she said on Twitter.
"We stand with US in defending the rights and freedoms of our citizens against those who spread hate."
An FBI Hostage Rescue Team stormed the synagogue in Colleyville, Texas on Saturday night. All the hostages were safely released and the gunman was dead, Colleyville Police Chief Michael Miller told a news conference.
Earlier Britain's foreign office confirmed the death of a British man in Texas, when asked to respond to a Sky News report that the gunman was a British national. The foreign office did not explicitly say the dead Briton was the gunman.
(Reporting by William James; Editing by Frances Kerry)
