ST. PAUL (AP) — A search warrant affidavit says a Minnesota man accused of killing a 9-year-old boy by firing at passing cars told investigators he did it because people had been waking him up by revving their engines.

Police found a note in Nhan Lap Tran's bedroom when they arrested him after the February rampage that read: "Random Kill, Fake Plates."

The affidavit filed in Washington County District Court says the date "12/12/12" was also scrawled on the bedroom walls.

Tran's attorney, Susan Drabek, did not immediately return a phone call to The Associated Press for comment Saturday.

The 34-year-old Tran is charged with six felonies in the Feb. 11 rampage.

Prosecutors say Tran had previously admitted to the shootings but hadn't given a motive.