The survivor had been raped by the watchman of the building, when she returned home in an inebriated state at 2 AM on Friday, police said.
"We have arrested the watchman of the society, identified as Pramod Upadhyaya (32)," a police officer said.
According to Powai police, the victim had gone to a nearby restaurant with two of her friends on Thursday night.
After the dinner, they hired an auto-rickshaw and went to drop her friend, after which her male friend dropped the victim near her building.
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Police further said that Upadhyaya had been keeping a watch on the victim for quite some time and have seen her coming home late from parties. However on Friday, he took advantage of the opportunity.
"After the act, Upadhyaya let the victim go to her house. However, she collapsed near the elevator after walking a few steps and was lying there throughout the night," said a police officer.
Police said that at 5 AM, the victim's brother found her lying on near the elevator lobby and took her to a doctor as she had bruises all over her body.
Police said that they had no leads in the case to work on as neither the victim could recall the incident properly nor there were any CCTV cameras showing the suspect.
However, the police got their first lead when they learnt that a watchman was missing.
"We first questioned a watchman but her said that he was guarding other portion of the complex and through him we learnt that there was one more watchman employed in the building. But he was missing", said an officer.
Interestingly, the police said that, the watchman did not attempt to run away as he was confident that the victim could never identify him.
However, following the arrest, he later confessed to the crime.
The accused has been booked under section 376 (rape) of Indian Penal Code and has been remanded to police custody till January 29.