CBS News learned that the woman died in a local hospital.
Hospital officials said two other people injured are in critical condition and were to undergo emergency surgery, according to the Canadian Broadcasting Corp.
The shooting at the college sent scores of the some 10,000 students at the college racing into the surrounding streets as they fled the campus. Some had clothes stained with blood.
Police spokesman Ean Lafreniere said there was just one gunman at the school and the search for any others was over.
Although police initially suggested the gunman had killed himself, Police Director Yvan DeLorme later said at a news conference that "based on current information, the suspect was killed by police."
CBC-TV showed police with guns drawn standing behind a police cruiser as a SWAT team swarmed the 12-acre campus. A bloody body covered in a yellow sheet lay next to a police cruiser near an entrance to a school building.
Montreal General Hospital said 11 people were admitted, including six who were in critical condition. The other nine were taken to two other hospitals.
Witnesses said a man wearing a black trench coat entered the school cafeteria and opened fire wordlessly.
Derick Osei, 19, said he was walking down the stairs to the second-floor cafeteria when he saw a man with a gun.
"He ... just started shooting up the place. I ran up to the third floor and I looked down and he was still shooting," Osei said. "He was hiding behind the vending machines and he came out with a gun and started pointing and pointed at me. So I ran up the stairs. I saw a girl get shot in the leg."
Osei said people in the cafeteria were all lying on the floor.
"I saw the gunman who was dressed in black and at that time he was shooting at people," student Michel Boyer told CTV. "I immediately hit the floor. It was probably one of the most frightening moments of my life."
"He was shooting randomly, I didn't know what he was shooting at, but everyone was screaming get out of the building," Boyer said. "Everybody was in tears. Everybody was so worried for their own safety for their own lives."
Raamias Hernandez, 19, said he had just finished his class when he saw everybody starting to run.
He said the gunman was dressed in a black jacket and had a mohawk haircut. Hernandez said he started to take pictures on a camera cell phone with his friend and the suspect saw them and started shooting.