Authorities are trying to figure out why a man killed his elderly parents before setting their New Jersey home on fire and turning the gun on himself.

The bodies of 76-year-old Richard Tempe, his 73-year-old wife, Barbara, and their 53-year-old son, Richard Jr., were found in their burning Fair Lawn home along with a handgun on Thursday.

Prosecutors say an autopsy determined the son killed his parents with the gun, set fire to the home and then killed himself.