Numerous photos apparently showed Gill posing with weapons
"Pathetic in life... even less in your miserable death," said one posting on the blog Kimveer Gill had set up on a goth culture website.
"I can't understand how you can kill people only because you think they suck!" said another.
Kimveer Gill was 25 years old and was from Quebec, according to the details he put on his profile on the website.
He introduced himself by saying: "His name is Trench. You will come to know him as the Angel of Death."
On Wednesday he entered a school in Montreal, in a trenchcoat and with a mohican haircut, and opened fire randomly.
One young woman was dead, several people were in critical condition, and more than a dozen others were injured by the time his rampage ended with his own death.
Police arriving on the scene exchanged fire with the gunman, but they believe Gill put a gun to his head and killed himself.
"He looked really mad... He looked like he really wanted to kill people," student Mathieu Dominique told the Canadian Press.
Gill's own postings on the site continued until 1041 (1441 GMT) Wednesday, only a few hours before he opened fire at Dawson College.
They said he had been drinking whisky, and that his mood was "crazy" and "postal".
There was little information on the killer except what he himself posted on his web profile, including what appeared to be his personal philosophy: "Work sucks... school sucks... life sucks."
The site carried numerous pictures showing the future killer dressed in a trenchcoat, brandishing a gun and a hunting knife, and in a red and white mask.
The pictures appeared to have been taken in a bedroom, which was adorned with gangster and horror film posters.
Some bore slogans expressing his anger.
One was a mocked-up gravestone with the epitaph: "Kimveer. Lived fast died young. Left a mangled corpse."
Another slogan proclaimed: "Life is like a video game, you gotta die sometime."
And it appeared Gill delighted in video games celebrating death.
Under "likes" he expresses admiration for Postal Dude, the player's character in the controversial computer game Postal.
The game's title derives from the American expression "going postal", used to refer to someone who goes on a shooting spree to exact revenge for some perceived slight or injustice.
The game, which has been banned in some countries, involves a series of mundane tasks that culminate in a bloodbath.
He also said he liked to play Super Columbine Massacre, an internet-based computer game based on the 1999 shootings at a Colorado high school in which 13 people were killed.
He posted the results of numerous "about yourself" quizzes on the site, one of which concluded that: "Your life is bleak and sinister. You feel anger at the world and you feel like the victim... However deep down you are lost and crying out for help."
In answer to a survey he said he had no fears, and that the goal he would most like to achieve this year was to "stay alive".Other answers included: Have you ever been in love? "Yes"; Do you get along with your parents: "No"; In the past month have you been on a date: "No"; How do you want to die: "Like Romeo and Juliet, or in a hail of gunfire."