FRANKFURT – German police arrested a man yesterday after two U.S. airmen were shot dead and two wounded in an incident on a U.S. Army bus at Frankfurt airport, authorities said.

Security round the airport was tightened and an investigation into the “terrible, senseless crime” was under way, said Boris Rhein, interior minister for Hesse state.

“Whether the incident was linked to terrorism, I cannot say at this stage,” he told reporters.