The fire incident took place in Shanti Nagar area of Shahdara on Thursday, resulting in deaths of Manoj (30), his wife Suman (28), and two girls, aged 5 and 3.
Two men were arrested for allegedly stabbing a 17-year-old boy in Delhi. The victim was attacked after he objected to one of the suspects' son harassing his niece.
Rohit Meena, deputy commissioner of police, Shahdara, said prima facie, it is a case of murder and attempt to murder by the man who later died by suicide.