A single word spoken by school principal Kallu Rupa Reddy shortly before her phone went silent helped Nalgonda police narrow their investigation to two of her students.Rupa Reddy, principal of Nagarjuna Grammar Concept School in Kondamallepally, was found murdered at her home in JB Colony on August 11. Police said she had suffered 27 stab wounds. Her husband, Rajender Reddy, was in Hyderabad on work at the time.The breakthrough came from the word “Babu”, which Rupa Reddy reportedly uttered while speaking to her aunt shortly before her phone was switched off.Investigators later learnt that the principal habitually addressed students at her school as “Babu”. This prompted police to examine the movements and behaviour of students following her death.Police examine CCTV footage, question 80 peopleNalgonda district SP Sharath Chandra Pawar constituted five special teams comprising around 40 police personnel to investigate the murder.According to The Hindu, investigators examined forensic evidence, fingerprints, dog-squad reports, CCTV footage, technical data and the movements of suspects. More than 80 people were questioned, while footage from around 70 CCTV cameras covering a 30-km radius was analysed.The school remained closed for six days after the principal’s death. After it reopened, police questioned students individually and monitored some students who had remained absent for two days.Five students who had reportedly shown sudden changes in lifestyle came under particular scrutiny.Two Class X students interceptedPolice subsequently matched CCTV footage from around the crime scene with the movements of the suspected students.On Wednesday, police intercepted two 16-year-old Class X students near Doniyala Crossroad at around 11.30 am. They were travelling by motorcycle from Pendlipakala Crossroad towards Mallepalli.A search allegedly led to the recovery of ₹1.54 lakh concealed in their undergarments. Police said three ₹500 notes had bloodstains.“When questioned about the money, the two allegedly confessed to killing Ms. Rupa Reddy and stealing cash from her house,” SP Sharath Chandra Pawar said, according to The Hindu.The two juveniles were students of the same school and shared a hostel room, police said.Principal had allegedly reprimanded studentsAccording to the police investigation, the two students had allegedly been caught with mobile phones and unaccounted cash in the hostel the previous month.Police said Rupa Reddy had reprimanded them in the presence of their parents. Investigators believe the incident led the students to develop a grudge against the principal.The students allegedly believed that Rupa Reddy kept a substantial amount of cash at home and subsequently decided to target her.Police said the two had also browsed social media and YouTube looking for ways to make quick money.Students allegedly planned murder for a weekInvestigators said the two juveniles allegedly conducted reconnaissance around Rupa Reddy’s house for about a week and researched ways to carry out the crime without leaving a digital trail.On the day before the murder, one of them allegedly went home from school to collect a red hoodie and trousers. The duo then allegedly bought a knife and gloves in Kondamallepally.On August 11, police said, the two reached a water tank near Rupa Reddy’s house. While one allegedly kept watch, the other entered through the open kitchen door.The two allegedly attacked the principal with knives and took Rs 2.5 lakh from her bedroom before escaping by jumping over the rear wall and fleeing through an isolated area.Police recover cash, knife and phonesAfter the alleged murder, the accused reportedly discarded the knife, gloves, mask and a mobile phone in bushes. They allegedly changed clothes nearby and threw the red hoodie into a drainage canal.Police said they subsequently recovered Rs 1.54 lakh, Rupa Reddy’s iPhone, the knife allegedly used in the murder, gloves, masks and two mobile phones from the juveniles.The case remains under investigation, with the police continuing to examine the evidence gathered from the crime scene and the suspects.