An imam and his assistant were shot dead as they walked along a street in the New York borough of Queens.
The men were approached from behind by a man who shot them both in the head, a police spokesman said.
Imam Maulama Akonjee, 55, moved to the city from Bangladesh two years ago, US media reported.
Some mosque-goers said they believed it was a hate crime but police said there was as yet no evidence that the men were targeted because of their faith.
A man holding a gun was seen leaving the scene of the shooting in the Ozone Park area, but no-one has been arrested.
Police said the suspect had a “medium complexion”. They released a sketch on Sunday.
Imam Akonjee and his assistant Thara Uddin, 64, were shot a short walk from the al-Furqan Jame mosque at about 13:50 local time (17:50 GMT) on Saturday.