By Anna Giaretelli, The Washington Examiner Michael Banks, the national chief of the Border Patrol, announced in a letter to employees Thursday that he will retire from his post. His resignation comes after a Washington Examiner investigation into unethical behavior as a federal agent, according to four sources familiar with the matter. “After over 37 years in public service to the people of the United States America, it is time for me to retire and return home to Texas to focus on my family and ranch,” Banks wrote in a letter to the workforce, obtained by the Washington Examiner. Banks led the 19,500-member Border Patrol for nearly 16 months since President Donald Trump took office, but he had faced scrutiny in light of the revelations about his personal conduct. Customs and Border Protection has not yet announced Banks’s sudden retirement.…