Tejas took the extreme step in the hall while his parents and younger sister were in other rooms of the two BHK flat on eighth floor of the 108 building in Tilak Nagar area, a police officer at Tilak Nagar police station said.
"The reason for the suicide is not yet clear and no suicide note was found," the officer added.
Hearing the bullet sound, Tejas's mother rushed to the hall and saw him in a pool of blood.
Tejas was immediately rushed to Rajawadi hospital where he was declared dead before admission. The body was later taken to J J hospital for post-mortem.
Police found a message on the deceased's WhatsApp Messenger that reads, "One day...No more for ever". The message was posted two days ago.
Police suspect that the third year Bachelor of Science student from Ruparel College might had an argument with his father before the killing.