India, Nov. 30 -- US homeland security secretary Kristi Noem on Sunday said investigators believe the man accused of fatally shooting a National Guard member and injuring another in Washington, DC, was radicalised after arriving in the United States.

Asked about the suspected gunman's motive on NBC's show, Noem said investigators were still building a full picture and speaking with people connected to him.

"But I will say we believe he was radicalised since he's been here in this country," she said, adding that his "home community and state" appeared to have played a role. She said officials were continuing to interview family members and contacts, noting, "So far we've had some participation."

Federal authorities have identified the s...