From the article:
"U.S. Border Patrol agents fired gunshots into Mexico after coming under attack during a half-ton drug bust and giving chase to a truck along the Rio Grande, U.S. authorities said Monday."
"No Border Patrol agents were hurt during the "fire fight" early Saturday in Mission, agency spokeswoman Rosalinda Huey said. She did not say whether Border Patrol gunfire hit anyone, citing the ongoing investigation."
"The firing they received came from the Mexican side," Huey said.