Ontario Provincial Police received a 911 call just before 11 a.m. Friday.
When officers arrived at a home on East Street at Petawawa Point near the Ottawa River, they found a man dead inside.
He has been identified as 56-year-old Danny Petersma.
Police said two females, ages 55 and 17, were critically injured and taken to hospital.
It was unclear if all three victims were found in the same home.
Helicopter, canine unit used in search
A helicopter and a canine unit, as well as officers on the ground, searched the town with assistance from military police for a suspect believed to be armed and dangerous.
Petawawa residents were told to stay inside and secure their homes while police combed the town searching for the suspect.
A 25-year-old man was arrested and charged with murder just before 1:30 p.m. It's not yet known whether the charge is first- or second-degree murder.
He was also was assessed by paramedics.
Police said the suspect has no fixed address and no connection to CFB Petawawa. He will appear in court on Saturday.
Several schools locked down during chaos
"[It was] chaos — police officers all over the place, flying up the hill because they heard something about guns at the school," said Petawawa resident Dan Reade.
"Traffic's been diverted all over the place, it's just been a hectic area around here right now."
The Renfrew County District School Board said in a statement that several of their Petawawa schools were placed on lockdown during the incident. The lockdown order was lifted around 2 p.m.
A man who lives on Abbie Lane, not far from East Street, told the CBC's Ryan Gibson that his dog started barking at the front door at about 10:30 a.m.
When he opened his door, he said, he saw a man he didn't know whose upper body was covered in blood.
The man said he shut the door and quickly called 911.