NEWARK, N.J. (AP) The two people who fatally shot a police officer then killed three people at a kosher grocery in Jersey City planned an assault for some time and were equipped to cause greater destruction, authorities said Monday.

State and federal law enforcement officials revealed details about the months leading up to the shootings by David Anderson and Francine Graham , a couple who expressed hatred of Jews and law enforcement in notes left at the grocery shooting scene and in online posts.

This was a senseless and cowardly act, U.S. Attorney Craig Carpenito said.

Anderson, 47, and Graham, 50, shot and killed Jersey City Detective Joseph Seals in a chance meeting in a cemetery Dec. 10, then drove to the market and killed Mindel Ferencz, 31, who owned the store with her husband; Moshe Deutsch, 24, a rabbinical student from Brooklyn who was shopping there; and store employee Douglas Miguel Rodriguez.