An attempted cellphone theft may be behind an incident that left a 16-year-old boy shot in the abdomen outside his Toronto high school and charged in connection with the case.

An adult -- Mark Deicsics, an 18-year-old Toronto resident -- has also been charged. They are both facing charges of committing an armed robbery while armed with a firearm.

The teen can't be named due to the provisions of the Youth Criminal Justice Act.

CTV News has learned that a group of teens were allegedly trying to rob another youth of a cellphone when shots were fired outside Bendale Business and Technical Institute on Tuesday.

It isn't clear if the person who fired the shot was being robbed or accidentally by a member of the victim's group.

Toronto Police Chief Bill Blair told CTV Toronto on Wednesday that police are still looking to speak with a third person who may have been at the scene of the shooting.

"I'm very confident that we are very close to quickly getting to the bottom of the events that led up to violence and that the people who are responsible for what took place will be dealt with appropriately," he said.

The 16-year-old teen is in stable but serious condition at Sunnybrook hospital after being shot outside Bendale Business and Technical Institute, a high school in the city's east end.

The shooting happened just before noon on Tuesday when many students were out on their lunch break in the Midland and Lawrence Avenues area.

A witness told reporters at the scene on Tuesday that he heard several shots being fired and then saw a group of people run into the school.

The victim stumbled inside the school and collapsed in a hallway where police found him.

On Wednesday, students and staff arrived at the school to find a number of crisis counsellors on hand to help them cope with the traumatic event, TDSB spokesperson Kelly Baker told CTV.ca.

However, a lot of students opted to take the day off.

One student who did come to school said he was still a bit nervous.

"I'm a little bit worried but my mom's more worried than I am," he said. "But I'm fine with coming back."

Gerry Connelly, the TDSB's director of education, said there are programs in place to help make schools safer but that unfortunately, there is never a guarantee against violence.

"We cannot guarantee 100 per cent that things won't happen but we are doing whatever we can," she said. "We have 27 cameras (around the school) and we have people looking after them."

Meanwhile, the president of the Canadian Safe Schools Network said the problem is a lack of funding for community support.

"Boards of Education and the government need to step up and provide more funding, more community assistance, more programs for these students," he said. "The benefits will be there if they can do this."

With a report from CTV Toronto's Galit Solomon