Gaziantep, Turkey (CNN) After the first airstrike hit near a hospital in eastern Idlib, Syria, no one was injured, according to one local man.

But then the warplane returned.

"Run, the plane is coming back," aid workers can be heard saying on video, right before the next explosion hits.

Activists say the incident was a "double-tap." That's when attackers strike, wait for first responders to arrive and then hit the same spot.

A dozen people were killed in the incident, which was caught on video by the Syrian Civil Defense, a humanitarian aid group.