On Saturday State police arrested 31-year-old Steven Colegrove.
He's from Deposit in Broome County.
Colegrove is charged with 3 counts of homicide.
This criminal complaint filed by Pennsylvania State Police explains why they believe he killed his family.
Investigators believe Joseph, Marlene and Michael Colegrove were ambushed in their home last Wednesday in Tuscarora Township.
Joseph and Michael were shot while asleep.
Marlene was killed in a hallway.
All 3 were shot in the head quickly and accurately.
Troopers say Steven Colegrove's has that shooting expertise based on his training in the military.
During questioning, State Police discovered a bruise on his shoulder.
It was the type of bruise typically left from firing a shotgun, the weapon used to kill the victims.
Investigators also say Steven Colegrove knew his parents home well, making it easier to get in and out.
But, a woman driving in the area around the time of the murders saw a pick up truck leaving the property.
Colegrove has a truck that fits her description.
Investigators point to money as possible motive.
His mother purchased a 100-thousand dollar life insurance policy in March of 2006.
Steven Colegrove would be the only child to receive benefits upon the deaths of his parents and brother.
Colegrove remains in the Bradford County Jail.
A preliminary hearing set for Wednesday was postponed.
The judge is on vacation.