The world is still in shock after Friday's terror attack in Stockholm, Sweden. Security expert Robert Strang told Inside Edition: "It is really hard to detect someone who is going to drive a truck into a crowd of people. So it really is worrisome and that is why intelligence is so important." Police in Sweden say the suspect, who hijacked a truck and rammed it into a major department store, is still at large. Three people were pronounced dead by authorities and nine others were said to be injured.