Calgary police said hard drugs were a common theme in three separate carjackings in the city on Saturday — one that saw a handgun produced, another that saw an elderly couple injured and a third that saw a suspect having to be sedated by paramedics.

Four people are facing charges.

The first carjacking happened just before 5 a.m., when officers were called to Country Hills Boulevard and Edgepark Boulevard N.W. A man driving a Toyota Tacoma was approached by two men while stopped at the intersection, police said.

The suspects were armed with a handgun and pointed it at the man while ordering him out of the truck, according to police. They fled in the vehicle.

Police said the suspects drove erratically away from the scene, veering into oncoming traffic.

When police tried to stop the vehicle at 14th Street and Fifth Avenue N.W., the truck rammed police vehicles and kept going.

The chase continued to the 1400 block of 14th Avenue N.W. where the vehicle was stopped and two suspects were arrested.

Second carjacking

Around noon, a man was seen acting erratically in the area of 37th Street near Bow Trail S.W.

"Acting out in traffic, running ... through traffic, kicking vehicles and [he] ultimately ended up trashing the inside of an Esso gas station," Staff Sgt. Rob Anderson said.

Four people were arrested after three separate carjackings in Calgary on Saturday. (David Bell/CBC)

About an hour later, the man jumped into the passenger seat of a car stopped at a light and assaulted the female driver before forcing her to drive a short distance. He then jumped out of the car and was arrested.

"[Officers] were forced to physically restrain him until ... paramedics with Calgary EMS attended and they had to chemically restrain him and transport him to hospital," Anderson said.

Chemical restraint is when paramedics administer a drug using a needle to calm someone down for their own safety.

The female driver was "struck in the head several times," said Anderson, and was treated for minor injuries.

Third carjacking

The third incident happened at about 2:30 p.m. as an elderly couple was walking toward their 2010 Ford Edge, which was parked in the 3400 block of 26 Avenue N.E., police said.

They were approached by a man who tried to get the car keys, which were attached to the elderly man's pants. The two began wrestling, police said.

The suspect managed to get the keys and drove off in the car, hitting the elderly woman and a nearby building in the process.

Both the man and woman suffered minor injuries. The woman had to be taken to hospital, Anderson said.

Soon after, witnesses reported the vehicle driving recklessly near Sarcee Trail and Richmond Road S.W. The HAWCS helicopter followed the vehicle to Highway 8 and Stone Pine Way S.W. where a man got out and was arrested.

Charges are pending in all three cases.

The level of violence used in the carjackings is concerning for police, Anderson said.

"Methamphetamine and fentanyl seem to be common denominators," he said. "Also, in a great number of [stolen] vehicles ... we're regularly seeing firearms, which is causing us to have more concern for public safety."

Anyone with information is asked to call police at 403-266-1234 or Crime Stoppers at 1-800-222-8477.