NEW YORK (Reuters) - A random fatal shooting in San Francisco, allegedly by an immigrant, proves the United States must tighten its borders, according to a statement on Friday by U.S. presidential candidate Donald Trump, who is facing heavy criticism for his comments about Mexicans. Kathryn Steinle, 32, was fatally shot as she walked with her father along the popular Embarcadero pier on Wednesday in what San Francisco police described as an apparent random attack. Francisco Sanchez, 45, was quickly arrested nearby. He is on probation from Texas, police said. He has a long criminal history and has been deported...