Murder Mystery Puzzles

To attend world science seminar, A famous chemist from Russia visit
Tokyo(Japan). In the lab, the scientist was killed and his six assistants were under suspicion of killing the chemist.
Name of six assistants: Austin, Wayne, Dege, Oscaru, Lingard, and Rojo.
He left a note “76-20-44 79-16-22-7”

A local detective L Lawliet was called to solve the case,

After reading the note, L Lawliet instantly asked the police to arrest the murderers.

Who are the murderers?

Your an Intelligence agent and you are assigned to the case of a murder. A man named John was murdered by someone in the house. You are to interview everyone that was in the house on Sunday at 6:30 pm. You interview the kids first you ask them “what were you doing on Sunday at 6:30” the kids said we were playing with our toys. You interview the wife and you ask the same thing. The wife says she was cleaning the kids room because the maid said she was going out with friends. Next you ask the maid, the maid says she was getting the mail. Who murdered Mr. John?