SALEM, Mass. (AP) — A Lowell man has been sentenced to life in prison after a jury found him guilty of using a shotgun to shoot a man in the head while he was sitting on his grandmother's front porch.

Rafael Martinez was convicted Wednesday in Salem Superior Court of first-degree murder for the July 2010 shooting of 20-year-old Timothy Walker in Lawrence.

Walker died two days after he was shot.

The case went unsolved for nearly a year until surveillance video of a man getting out of an SUV, walking down the street, and opening fire was aired on television. That generated tips that led to the 21-year-old Martinez's arrest.

Martinez's lawyer said there was little evidence in the case and the face of the man in the surveillance video was not clear.