Damodaran slit the throats of his victims one after the other before trying to cut his neck himself, police said.
He was rushed to a hospital, where he is undergoing treatment.
Damodaran's wife was 37 years old, the son was aged eight years,his daughter was five and his mother was in her sixties.
"Damodaran had borrowed loans running to lakhs of Rupees from his brother-in-law Raja and was depressed that he could not repay it," Police Deputy Commissioner (St Thomas Mount) M S Muthusamy told reporters.
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He said Damodaran's brother-in-law did not demand repayment of loan and in fact continued to render all help and support.
Damodoran was still depressed, more so by losses he sufered in his business.
To a question, Muthusamy told PTI, "Damodaran is out of danger now. We have booked a case of murder against him."
He said Damodaran rang up Raja before slitting his throat and told him he was going to commit suicide.
Raja and other relatives rushed to the house and found all of them lying in a pool of blood.
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