Premise: U.S. President Donald Trump on Monday called for tighter restrictions on immigration in the wake of the terrorist attack in New York City carried out by a Bangladesh native living in the U.S. "America must fix its lax immigration system, which allows far too many dangerous, inadequately vetted people to access our country," Trump said in a written statement quoted by USA Today.
Hypothesis: Improper and ill-informed background checkup of the foreign citizens have allowed dangerous immigrants to enter the US under the current immigration system, that must be fixed said Donald Trump, to avoid catastrophic events like that happened in New York City.