Suicide bomber Salman Abedi was ejected from a Manchester mosque after a row in which he was accused of behaving like a child.
The dispute two months ago at the Salaam Community center in Moss Side came after he had tried to hide in the mosque library to read religious books overnight.
Mosque chairman Abdullah Muhsin Norris, 70, told Sky News: "I am very unhappy knowing that he has come here and prayed here and seeing him reading the Koran and so on and the next minute you hear he blew up and 22 people are killed ... It is very hard to believe someone could do that, but he has done it."
On the incident two months ago, he said: "I saw him staying over in the mosque and I told him that he had to leave."
"I was very annoyed with him. He said don't treat me like a child.
"He is very easy to be upset."
The chairman told Sky News he has banned political discussions at the mosque and has previously referred matters to the police where he has been concerned about radicalization.