Double teen murder 'terrible, shocking':PM

Malcolm Turnbull has described as "heartbreaking" and "shocking" the murder of two teenage children by their father in Sydney's northwest.

John Edwards, 68, was found dead in his home hours after killing his 15-year-old son and 13-year-old at their West Pennant Hills house on Thursday evening.

"It's a terrible, terrible tragedy," the prime minister told reporters on Friday.

"Our hearts go out to the mother and to all of the family.

"We mourn the loss of those young people and pray that those who have been so, so hurt by this shocking crime can find comfort in prayer and the consolation from friends and loved ones."