An online video game that recreates the Dawson College shooting has upset students at the Montreal post-secondary institution. (CBC)Montreal police are investigating an online video game that replicates the shooting rampage at Dawson College that killed a student and injured several more four years ago.

Students at the post-secondary college said they're shocked anyone would create a game about the violent tragedy.

Anastasia DeSousa, 18, was killed and 19 other students were injured when a gunman opened fire at the downtown CÉGEP college in September 2006. The gunman killed himself in the school.

The aim of the free online game is to "storm Dawson College with your favourite rifle, and kill those students and kill any cops you can," according to one of the sites where it is available.

A slide show featuring pictures of the gunman and his collection of weapons also shows quotes he published on his blog prior to his attack at the college.

When the game begins, players have to fire at as many students as possible before police arrive.

Each time a player manages to shoot a student, there's a burst of blood, and the student dies screaming. Eventually, police show up and start to fire their guns.

When the player is hit, the game zooms in on the back of the pixelated character as it shoots itself in the head.

Game upsets students

News of the game's existence has upset many students at the college.

Dawson nursing student Laura James said she couldn't understand why anyone would invent such a thing. "I couldn't believe it," she told CBC News. "I was like honestly shocked because why would someone do that?"

The game is insensitive to survivors, said student Serina Galle. "It can hurt people. If someone just falls upon this site that was actually there they could be reliving something that's like really traumatizing in their life," she said on Tuesday. "No one wants to relive that."

The man who made the game is 23, lives in Ontario, and goes by the online name "Virtuaman." When CBC News contacted him, he said he was sorry he offended anybody, explaining he only wanted to draw attention to the reality of school shootings.

"I didn't make it to be a sicko or anything. I didn't wanna offend the families or any of that, but I guess it's going to. It's pretty graphic," he said, adding he believes he's broken no laws.

The student union at Dawson has contacted one of the gaming sites where the game is available and requested it be removed, which it agreed to do. But it is still available on three other sites.

It's not the first video game created after a school shooting.

Following the Columbine School shooting in the U.S. in 1999, a similar game appeared.

The gunman who attacked Dawson College admitted he played that game prior to going on his rampage in Montreal.