Who is the killer?
Tarun Asthaniya is found dead in his office at his desk. The police have narrowed the suspects down to three people: Mrs. Harish Kumar, Taruns wife Himanshi Asthaniya and his buisness partner Mr. Jason Negi . All three visited Tarun on the day of his murder, but all three provide the police with stories of explanation as to the reason for their visit.
Police found Mr. tarun with his wrist watch still on his right arm, a torn up picture of his wife laying on the floor beside the trash can, and an ink pen in his right hand. On the desk, the police found a name plate, a telephone that was off the hook, and a personal calendar turned to the July 5th page with 7B91011 written on it. After examining this evidence, the police knew their suspect. Who was it ?

Fun fact:
Octopuses have four pairs of arms.