id. At least two people were hospitalized, and the suspected shooter was killed shortly after officers arrived. Authorities have not confirmed the severity of the victims' injuries or who fatally shot the suspect.

The victims

Three children - ages 5, 8 and 11 - and an adult teacher were killed. Their identities were not publicly disclosed, but their families were notified, Krantz said.

A 7-year-old and a 54-year-old teacher were taken to St. Charles Medical Center - Bend with critical injuries, he said.

What we know about the suspect

Officials identified the suspect as a 16-year-old Bend resident but did not disclose his name.

Authorities declined to say how many shots were fired.

A Bend resident who was walking near the school Thursday afternoon heard at least six shots ring out.

 They were spaced out, which made us question whether it was gunshots or someone doing construction,  Leah Schwartz told NBC News.

AP Photo/Joe Kline AP Photo/Joe Kline

Police said they are still investigating the suspect and did not say whether he previously attended the school or knew anyone who did.

The Bureau of Alcohol, Tobacco, Firearms and Explosives received the results of an urgent trace on the long gun used by the gunman Thursday evening, a source familiar with the investigation and the crime scene said.

Authorities have not said how the shooter got access to the weapon. In Oregon, a person must be 18 to purchase rifles and shotguns and 21 for handguns. It is illegal to sell firearms to minors.

However, people under 18 can legally possess firearms if they have parental consent, in which case they may use non-handgun firearms. Minors can also temporarily possess firearms for lawful reasons, such as hunting or target practice.

The investigation

Krantz said there will be a large law enforcement presence at the school for several days.

 This is going to be a long investigation,  he said.

Kotek, the governor, said that the Oregon Department of Emergency Management is coordinating across multiple state agencies and that  the state stands ready to support  the community. The ATF and the FBI were also assisting.

All schools in the Bend-La Pine Schools district, as well as activities and athletic events, are canceled Friday.

Bend Mayor Melanie Kebler said Thursday that it was an  awful day for our community. 

 A school should be a safe place where children can learn and feel secure,  she said.