It was just another Friday night in the young life of 18-year-old Sammy Yatim — until he was shot nine times by a police officer for brandishing a small knife inside an empty streetcar.

Despite the existence of at least three videos that capture the exact moment Sammy was gunned down by an as-yet-unidentified Toronto Police officer while standing inside an empty downtown tram holding a two-inch blade, many questions remain unresolved.

Here's what we do know:

Sammy, a Syrian immigrant, moved to Toronto with his dad five years ago after his parents got divorced. His mom still lives in Aleppo.

He had recently graduated from Brebeuf College School and was preparing to start college in the fall.

He recently moved out of his house and into the home of a friend after a disagreement with his dad over his future, as well as a penchant he developed for smoking pot.

A knife collector by hobby, Sammy was a "quiet, respectful guy," who was in the process of getting his life back on track after some setbacks.

He had hung out with some friends at the mall on Friday, and was on his way home when he apparently got sidetracked.

Just after midnight, Sammy boarded a streetcar on Dundas St., took out his knife, exposed himself, and ordered all the passengers to leave.

Police officers soon arrived at the scene and shot him to death.

[There was a video here]

Here's what we don't know:

There is no record of Sammy's whereabouts or activities between 10 PM, when he phoned a friend to say he was heading back to the apartment, and Midnight, when the confrontation with police was set in motion.

It is unclear what set him off, and why he ignored officers' requests to drop the knife. (A witness to the incident said Sammy looked "like he was shocked.")

We also don't know why 23 officers felt their lives were put in jeopardy by a teenager with a pocket knife standing like a deer in headlights inside an empty public transportation vehicle.

And the most critical question of all: Why was it necessary to fire nine bullets into Sammy's upper torso — several of which were discharged after he had already dropped — and then Taser his lifeless body.

"I am very aware that the public is very concerned about this tragic event," Toronto Police Chief Bill Blair told reporters at a press conference today. "They have every right to be concerned."

Blair said the law prevented him from answering questions while an internal investigation was ongoing, but a police spokesman revealed that the police officer who killed Sammy had been put on paid leave.

The Toronto Police Association president said the officer, a six-year vet, was "devastated" by the incident, and insisted that the videos offer "one slice of a bigger picture."

Meanwhile, Toronto is on the cusp of boiling over, with hundreds taking to the streets to express their outrage over Sammy's death.

"There’s no reason for this guy to be dead. There’s no reason," said a friend of the family who attended the vigil. "Police – they are professional, they are trained. They can’t handle a two-inch knife? How they’re gonna handle something else?"

[screengrab, video via YouTube, photo via Facebook]