New Delhi, Sept. 24 -- The lack of patrolling and security infrastructure inside the 142-acre Aastha Kunj Park near Kalkaji Temple apparently made it possible for the three men to gang-rape a 17-year-old on gunpoint, despite one of them having been previously seen carrying a knife and harassing couples by locals in the area. While several people had verbally reported them to the facility's staff and guards, investigators aware of the details of the case said on Wednesday that they had not filed any official complaints in the matter. The horrific crime took place around 7.15pm-7.30pm on Monday while the girl, a Class 11 student, along with a 17-year-old male friend, were visiting the park on her 17th birthday. Police identified the accused as Asif, 30, and brothers Mukesh Singh, 24, and Hemant Singh, 31. "We found that people mostly complained that Asif was generally seen with a knife. Also, we are probing allegations that the three would harass some couples. This was never reported to us, so we are looking for more proof," said a senior police officer. Staff members and guards from the park as well as a nearby godown, and regular visitors identified Asif in particular as a local troublemaker, said police. On Tuesday morning, Asif was apprehended first, around 6 am, from Amar Colony after a brief exchange of fire. An unlicensed firearm and a knife were found in his possession. Later, Mukesh and Hemant were arrested from their home in Sri Niwaspuri. Police said they are probing whether the men used the same modus operandi to target other women in the park. "Asif and his associates have been seen coming from Okhla Mandi area with a knife and roaming around the park at night. They are regulars at the park," said a second senior police officer. On the day of the incident, the officer said, they were carrying at least two weapons -a firearm and a knife - and condoms with them. "We have suspicion that this was planned." Park staff and others are being questioned for more details. During the interrogation, they told police that they had been roaming around for nearly 45 minutes looking for a target when they saw the minors sitting in a secluded spot. Judging them to be easy targets, the three then decided to threaten them by posing as policemen, said the second officer. The first officer said that after scanning CCTV footage from peripheral areas and going through their call detail records, police were able to trace the movements of the three men from after the incident. "While Asif learnt from locals that the police were looking for him and decided to escape, the two brothers were roaming around," the officer said. The two brothers went to a restaurant to eat first. Then they returned home in the Sri Niwaspuri area, where they washed their clothes to get rid of all the evidence. "When we arrested them around 7 am on Tuesday, their washed clothes were found nearby. We also seized their phone but found they had deleted a lot of media recently. The FSL (Forensic Science Laboratory) will try to recover the data," the officer added. Police also found "objectionable" and pornographic content on Asif's phone and have asked FSL to file a report. Asif worked at the Okhla Sabzi Mandi and allegedly had been carrying an old unlicensed firearm for years. Police are verifying Hemant's claims that he has studied law from a public university in Rohtak, graduating in 2014-2015, and was presently preparing for competitive exams, said the police. They are also verifying allegations that he was removed from a gym near Garhi village about a month ago after its management allegedly received several complaints from women regarding his behaviour. Police said they have spoken to staff, but have still to question the gym owner. Mukesh is a final-year student of B.Sc (Maths) at a college in Palwal. Locals in Sri Niwaspuri said they were "not too shocked" to hear about the news of the two brothers being arrested in a gang-rape case....