GAZA CITY — Hassan al-Zeyada has spent decades counseling fellow residents of the Gaza Strip who experience psychological trauma. Now, as he prepares to aid his neighbors after a new round of combat and carnage, he has a challenging new patient: himself.

An Israeli airstrike demolished Dr. Zeyada’s family home on July 20, killing six close relatives, including his mother and three of his brothers.

“You try to help the people with their suffering,” the doctor said recently in his Gaza City living room, lined with psychology textbooks. “It’s totally different when you have the same experience. You lose six from your family — three brothers, your mom, one of your nephews, your sister-in-law. It’s really” — he paused, red-eyed — “unexpected.”

He took a mental step back, to diagnose the hallmarks of trauma in himself: He was exhibiting dissociation, speaking in the second person to distance himself from pain, as well as denial. When he heard about new shelling near where his family lived in the Bureij refugee camp, he picked up the phone to call his oldest brother there. He had forgotten that the house was already gone, his brother already dead.