Combat training is a rite of passage for police recruits. It's left a trail of deaths and injuries

Heather Sterling stepped into the ring at the Texas Game Warden Training Center, ready to face an ambush by instructors acting as violent assailants. The four-on-one drill is a rite of passage for those training to be game wardens, sworn officers who enforce state conservation laws. Nationwide, thousands of local and state police recruits are allowed into the profession only after passing similar drills – simulated fights for their lives.