Fridge / Rampage (2009)

• How did Evan's dad know it was Bill?
  • Bill had the guns shipped to Evan's house instead of his own. While neither Evan nor his dad knew what was in the boxes, it's possible that his dad put 2 and 2 together after the town was massacred, and his son was killed in an apparent suicide. He could've realized that "hey, those were guns in the boxes that Bill had shipped to our house, and he framed my son!"
• Even though Bill framed Evan and his father, in the sequel somehow it's been discovered he committed the massacre and is now a wanted fugitive on the lam.
  • He did upload a video of himself almost confessing that he killed all of those people, which went viral, so it was probably connected.
  • Most likely, the frame job only held up for a few days. The police would eventually have found who actually owned the guns and armor, that Evan did not actually shoot himself, and so on. By then, of course, Bill would have been long gone.