A 20-year-old woman who was cut off by another motorist in Lowell on Thursday allegedly took revenge by fatally shooting him. Then she bragged about it on Facebook, saying she had warned the victim and his co-worker, "Don't make me spank you," authorities said.

Middlesex District Attorney Marian T. Ryan said it appeared to be a "random encounter in traffic" and "possible road rage" that led to the shooting of Marc Devoe, 34, of Peabody.

Graciela Paulino of Lowell was arrested shortly before 11 p.m. Thursday and charged with murdering Devoe, Ryan said.