The bus was full of children returning from school as an unidentified gunman opened fire on the vehicle killing three and injuring another.
Russian Investigative Committee, the agency that handles major crimes, says the shooter has been identified as a student at the university.
Police say the shooting appeared to be a"targeted event not a random shooting", and the intended target was an employee who was not there at the time but the gunman decided to shoot some of their friends or acquaintances.
Vaccine teams and security forces escorting them are often targeted in attacks in Pakistan, one of three countries where the crippling disease remains. The Taliban claims the preventive drug is a Western conspiracy to sterilise children.
Abdul Aziz is being hailed as a hero for preventing more deaths at the Linwood mosque in Christchurch after leading the gunman in a cat-and-mouse chase before scaring him into speeding away in his car.
The Russian Investigative Committee says an 18-year-old student identified as Vladislav Roslyakov arrived a vocational college in the Crimean city of Kerch with a rifle and killed 19 people.
A gunman took hostages inside a supermarket in the US city of Los Angeles on Saturday and shot one woman dead before handcuffing himself and surrendering.
The motives behind the the incident, in which the assailant had also taken a woman hostage and injured two more people, remain unclear.
A manhunt is underway for a 29-year old man who killed four people at a waffle house in the US city of Nashville in the early hours of Sunday.
Police in Texas said Sunday they were seeking a person of interest in an overnight shooting that killed a young woman and wounded four other people.
The 18-year-old German-Iranian student, David Ali Sonboly, who killed nine people in a shooting rampage in Munich, Germany had been planning the attack for a year.
An unidentified gunman with an unknown motive has been killed after taken hostages in a cinema in western Germany.
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