This article says:

“The Israelis have said this is a tragic mistake,” Kirby said, referring to the airstrike and fire in an area crowded with refugee tents that Gaza health authorities said killed at least 45 people on Sunday.

According to an AP article titled: Netanyahu says deadly Israeli strike in Rafah was the result of a ‘tragic mishap’

Netanyahu did not elaborate on the error.

That’s a blank statement. So what does Netanyahu consider as a mistake? Bombing too little?