Insider attack. Update to this previous story.

Via ABC News:

Four Americans were killed and 17 troops and contractors were wounded while participating in a Veterans Day 5K run when an apparent lone attacker managed to detonate a deadly bomb inside the sprawling Bagram military base in Afghanistan yesterday, counterterrorism officials told ABC News today.

The U.S. military’s Operation Resolute Support provided few details beyond confirming that a blast inside the base had left two U.S. service members and two American contractors dead along with 16 American troops and a Polish trooper wounded.

Bagram Airfield is home to nearly 14,000 military forces and contractors.

But officials in Washington and various U.S. military commands have been told that the victims were participating in a 5K run celebrating Veterans Day, two counterterrorism officials told ABC News.

A coalition official later told ABC News that the attacker used a belt or vest bomb in the attack.

The attacker was a former Taliban militant who had joined the peace process in 2008 and had since taken a job at the base, Bagram District Governor Haji Abdul Shokor Qudosi told ABC News on Sunday.

Neither the exact nature of the attacker’s work on the base, nor when he began working there is known. It is common for local residents to take jobs like day laborers, cleaners and cook assistants at the facility.

Keep reading…