Police say a man sealed all the windows and doors of his parents' home, then filled the sinks and tubs with bleach and ammonia in an attempt to harm himself and his family.
Officers responded to the home in the 400 block of Dickinson Road in Deptford just after 10 p.m. Saturday for a report of an unconscious 21-year-old man.
Investigators say the man's father found him and called for help.
Arriving police and medics became short of breath and had to leave the home.
The man was placed in critical condition at an area hosptial.
His parents, sister, her boyfriend and the first responders all had to be treated at the hospital. All three are expected to be okay.
"I looked out the door and started smelling an ungodly smell... I was thinking it smelled like sewer gases or something chemical and it was taking my breath away a little bit," said a neighbor.
Deptford Township police and the Gloucester County Prosecutor's Office are investigating the incident.