The shooting took place at Silver Rail Elementary School in Bend on Thursday, with police saying that children were among the victims.
Bend Police Department chief Mike Krantz said at a press conference that officers received dozens of calls that a suspect armed with a long gun had entered the school building.
Shortly after 1.02pm (9.02pm UK time), he said officers found that the suspect had been shot and killed by a member of the public who pursued them into the school.
After this, police found that four people - three children aged five, eight and 11, and one teacher - had died.
Another child, seven, and a teacher were taken to hospital, Mr Krantz said, adding that the suspect was 16 years old.
Police responded to the Oregon school at about 1pm local time after a first call reporting a gunshot being fired into a car.
Speaking at a press conference with the police chief, superintendent of Bend-La Pine Schools Steve Cook added that classes, activities and athletic events across the school group have been cancelled for Friday.
Bend mayor Melanie Kebler also said "a school should be a safe place... what happened today should never happen" - while also announcing a community vigil.
Sheila Miller, a spokesperson for the Bend Police Department, told reporters earlier that Silver Rail Elementary School serves kindergarten through fifth grade, roughly ages five to 11, and has about 450 students and 40 staff members.
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Oregon governor Tina Kotek said earlier on Facebook that "we must come together and support each other, neighbour to neighbour, Oregonian to Oregonian" following the "tragic event".
At the press conference, she also praised the community member who shot the suspect in the shooting.
FBI chief Kash Patel said on X that federal agents were on the scene "assisting our local partners in the investigation" and that his agency would "make every resource they need available."
The collision between the minibus and freight train happened on Thursday evening, French authorities said, adding that none of the injuries were life-threatening.
According to reports in France, the minibus was carrying 19 people, including the driver. Two of those are in serious condition, they added.
Ambulances, firefighters, police and a helicopter were scrambled to the scene.
The freight train was stationary near the entrance to the Channel Tunnel - and the bus was carrying truck drivers who were preparing to board the Le Shuttle service on the loading platform at the Eurotunnel site.
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The drivers were of different nationalities and were all male.
Officials added that it was the first time that an accident of "this type" had occurred on a Eurotunnel loading dock.
Authorities did not immediately provide more details on how the accident happened.
An image of the scene in French media shows the bus heavily damaged, with police and medics crowding around the scene.
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There was not expected to be any disruption to Eurostar journeys despite the incident.
The rail operator said in a status update: "This incident does not involve or impact Eurostar trains running from and to London.
"All of Eurostar trains will run as expected."
It added the collision "occurred several kilometres away from the Channel Tunnel".
Vickrum Digwa was jailed for life for stabbing 18-year-old Mr Nowak to death in Southampton on 3 December last year.
His mother, Kiran Kaur, arrived at the scene and removed the knife used by her son before police arrived.
Kaur was sentenced to three years in prison for assisting an offender in July, having taken the weapon back to the nearby family home.
Sky News understands that the release is set to take place in December, with Kaur, an Indian national, possibly being eligible for the government's deportation scheme.
The Home Office declined to comment on individual cases, but said: "Our thoughts remain with the family and friends of Henry Nowak, whose life was cruelly cut short in a horrific act of violence.
"We will always seek to deport foreign criminals at the first opportunity."
Kaur could serve less than half of her sentence, and be freed around the anniversary of Mr Nowak's death under the government's early release scheme.
She is also appealing against her punishment, with a hearing scheduled at the Court of Appeal on 5 November.
When her sentence was imposed, the 221 days she had already spent on remand were taken into account, it is understood.
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Some 5,000 prisoners are scheduled to be released in stages over the next year, down from 6,000 after ministers intervened to exempt rapists and the most serious child sex offenders.
Mr Nowak, a first-year finance student from Chafford Hundred, Essex, had been on a night out with his football team.
He was knifed five times by Digwa, suffering four stab wounds and a cut to his jaw, a post-mortem found.
But, despite his injuries, he was mistakenly arrested and handcuffed by police officers who believed Digwa's claim that Mr Nowak had racially abused him.
Hampshire Police later apologised for their officers' error.
Philip and Kim English were killed in the fire in Waterford shortly after 5am on Tuesday.
Two children, named Callum and Jayden, also died, while two more children with critical injuries were taken to hospital in Dublin.
On Thursday, police arrested a man in his 20s and a woman in her 30s over the incident.
Gardai said the duo were arrested on suspicion of facilitating a criminal organisation.
Police believe the blaze was started deliberately and have begun a murder investigation.
A post-mortem examination on Mr and Mrs English and the children has been completed but the results are not being released for "operational reasons".
Gardai have repeated their appeal for information on the suspected attack which took place on Birch Avenue, Birchwood.
On Thursday, Sinn Féin TD David Cullinane said the suspected attack showed "utter contempt for human life".
Multiple properties have been searched with a number of electronic devices and vehicles seized as part of an "intense" Garda investigation.
Hundreds attended a vigil on Wednesday in the Birchwood area.
A post-mortem examination found William Chapman, 24, died from multiple traumatic injuries after entering the enclosure of Amur tiger Altai at the park in Doncaster, South Yorkshire, on Saturday.
The park said in a statement: "Yorkshire Wildlife Park will reopen tomorrow (Friday) following the tragic incident that occurred at the park on Saturday.
"Our thoughts and heartfelt sympathies remain with the family, friends and loved ones of William Chapman who sadly lost his life.
"The safety and wellbeing of our visitors, staff team and animals remain our highest priority. We would like to thank all the people who have emailed, commented on our social media or contacted us with messages of support and love for our team at this time."
The park added: "Many people also contacted us about Altai, the tiger. We can reassure everyone that he is safe and well and will not be euthanised as a result of this incident."
Land Of The Tigers will reopen to visitors following engagement with the relevant authorities, the park said.
The park praised the "professionalism" of its staff ahead of the reopening.
"As we welcome visitors back, we would ask everyone to be understanding and respectful towards our staff team, who have shown tremendous professionalism and dedication during an exceptionally difficult time," the statement added.
"We are providing specialist trauma support and ongoing care for those affected. As enquiries remain ongoing, it would be inappropriate for us to comment further on circumstances at this time.
"We would like to thank everyone for their patience, understanding and support during this difficult period, and we look forward to welcoming visitors back to the Park."
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An inquest into Mr Chapman's death, which opened on Thursday, heard that he had previously been diagnosed with schizophrenia and suffered bouts of psychosis.
His family had expressed concerns about his contact with mental health services before his death, Doncaster Coroner's Court was told.