Ms Halonen called the incident shocking and sad.
'We have to have very serious discussions and studies on what to do,' she told a news conference on the sidelines of the UN General Assembly last night.
Among the topics for discussion will be gun control and the differences between hunting rifles and handguns, said Foreign Minister Alexander Stubb.
In an echo of last year's deadly attack at a high school in Finland in which eight people died, the gunman in yesterday's incident, 22-year-old Matti Saari, posted menacing comments and videos of himself wielding a gun on the Internet before going on the shooting rampage.
He shot nine students and a teacher at the college about 330km northwest of Helsinki, before turning the gun on himself. He died later in hospital from his injuries.
'Finland is a northern country with large areas of nature and hunting is one of the common hobbies, and so of course there are thousands and thousands of people who do it quite legally. But that means also that many people have many weapons,' Ms Halonen said.
She said that although the Internet and Web discussion forums were the domain of the younger generation, adults 'should also be active and see that the rules in real life are also the rules that people have to respect in all circumstances. We have to follow the situation there.'
Change to gun age limit not implemented
Mr Stubb said the government is discussing the issue of possible gun controls in the country, where gun ownership rates are among the highest in the world, but crime rates in general are low.
'Basically we are in the process of discussing the matter,' Mr Stubb said in response to a question. 'There is a handgun directive which is channelled through the European Union and our legislation falls within the realm of that legislation.'
Finland, the minister said, has very strict gun laws despite a high number of 1.6m registered arms in the country of about 5m people.
'But I am sure that now in Finland we will start a discussion also on the difference of what could be called hunting rifles and just basic traditional handguns. This discussion will start now after the incident.'
Officials in Finland said police were in contact with the gunman a day before the shooting after they were alerted to his Web footage. He had a temporary permit for a pistol.
Mr Stubb noted that a government plan to raise the minimum age for gun ownership to 18 from 15 after last year's shooting had not taken effect but added: 'I am sure this whole package with the arms will be reopened after this incident.'
